Stratigraphic and temporal context and faunal diversity of Permian-Jurassic continental Tetrapod assemblages from the Fundy rift basin, eastern Canada.
The early Mesozoic was a time of extreme geography and climate. The supercontinent Pangaea nearly symmetrically straddled the palaeoequator (Fig. 1). With no evidence of polar ice (Sellwood and Valdes 2006), this 'hothouse' world was marked by coal deposition in polar and equatorial regions and by arid conditions in subtropical regions. Soil carbonate CO2 proxies from eastern North American rift basins and elsewhere indicate that Late Triassic background concentrations of atmospheric CO2 were between 2000 and 3000 ppm (Tanner et al. 2001; Schaller et al. 2011, 2012), whereas the leaf stomata CO2 proxies yield lower, but still impressive, concentrations of about 1000 ppm (McElwain et al. 1999; Steinthorsdottir et al. 2011). Despite vast climatic differences compared to the present day there existed a humid equatorial zone of apparently modern dimensions (Kent and Olsen 2000). As Pangaea drifted northward, the Fundy basin passed through the transition zone between this humid region and the arid subtropics to the north, recording the Triassic-Jurassic transition and temporally adjacent events.
The material referred to in this paper is lodged at several institutions, referred to by abbreviations as follows: FGM, Fundy Geological Museum, Parrsboro, Nova Scotia, Canada; MCZ, Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, U.S.A.; NSM, Nova Scotia Museum of Natural History, Halifax, Nova Scotia, Canada; ROM, Royal Ontario Museum, Toronto, Ontario, Canada; and YPM VPPU, former vertebrate palaeontology collection of the Museum of Natural History of Princeton University, now housed at the Peabody Museum of Natural History, Yale University, New Haven, Connecticut, U.S.A.
The Canadian Maritimes have a long tradition of geological research. The eminent Canadian geologist John William Dawson was the first to study the geological structure of the region, especially of his home province of Nova Scotia, in a systematic fashion; he also pioneered the collection of fossils from a wide range of strata and localities. On a field trip with Charles Lyell, Dawson discovered the now-famous occurrence of tetrapods within stumps of Pennsylvanian-age arborescent lycopsids at Joggins, Nova Scotia, in 1852. Later he summarized his observations, as well as data from other researchers, in his classic Acadian Geology, which went through four editions between 1855 and 1891 (Dawson 1855, 1891). Dawson was first to illustrate the complex outcrops of the Triassic-Jurassic rocks along the northern shores of the Minas Basin, including Wasson Bluff, a locality that would prove critical to understanding the Triassic-Jurassic transition in continental biotas worldwide.
The next major contribution of significance was the study of the "Acadian Triassic" in Nova Scotia and New Brunswick by Sidney Powers, which resulted in a doctoral dissertation at Harvard University (Powers 1915, 1916). Based on his own extensive fieldwork and careful review of earlier studies, Powers laid the foundation for all subsequent research.
In the late 1950s William Take, then Curator of Geology at the Nova Scotia Museum of Science in Halifax, was the first to discover vertebrate fossils in exposures of the Triassic Wolfville Formation in Hants County, Nova Scotia, in what we term the Evangeline Member (see below). In late 1958 he showed his finds to Donald Baird, then Curator at the Museum of Natural History at Princeton University. Baird and Take followed up on the latter's discovery and collected additional vertebrate remains and other fossils from the Wolfville Formation in 1959 and 1960 (Baird and Take 1959). Although their collaboration did not continue after 1960, Baird continued to collect material from the Wolfville Formation until 1985 (Baird 1963; Baird and Olsen 1983; Sues et al. 2013). In August 1966, Baird discovered another occurrence of Triassic vertebrate fossils near Lower Economy in Colchester County, Nova Scotia, in what we identify here as the Economy Member (see below). Although most of the material from this locality is dissociated and fragmentary, the composition of this faunal assemblage is distinct from that collected by Baird and Take from the Wolfville Formation along the southern margin of the Minas Basin. Baird later collaborated with other researchers to prepare a detailed guidebook for a field excursion to key localities with fossil vertebrates in eastern Canada for the Twenty-Fourth International Geological Congress (Carroll et al. 1972).
Although Baird never published extensively on his discoveries of early Mesozoic tetrapod fossils in Nova Scotia and New Brunswick, he kept meticulous records for most of his active research career, spanning the period from March 1953 through August 1998. In August 2011, Baird's son Andrew and the scientific executor of Baird's estate, Robert Hook, donated five notebooks to the Society of Vertebrate Paleontology Archive at the Smithsonian Institution Archives (SIA Accession Number 12-107) (Sues et al. 2013). These notebooks have continuous pagination, and thus we will cite them in the text as "(Baird MS, page number)".
In August 1976, one of us (PEO) discovered fragments of bone while prospecting exposures of the McCoy Brook Formation near Parrsboro, Cumberland County, Nova Scotia, while travelling with the Baird field party (Baird MS, pp. 574-575). When reassembled, this find proved to be a cervical vertebra of a sauropodomorph dinosaur. In 1984, PEO found a well-preserved partial skull of a sphenodontian reptile near the same spot. Over the years, various researchers, most recently Tim Fedak (Fundy Geological Museum), have collected additional skeletal remains of sauropodomorphs. PEO's discovery prompted a major research effort during the 1980s by teams from Columbia and Harvard universities led by himself and Neil Shubin. The result was the discovery of diverse vertebrates from aquatic to fully terrestrial depositional settings (Olsen et al. 1989, 2005a, b; Shubin et al. 1991, 1994; Sues et al. 1994, 1996). Subsequently, the present authors and others have continued to explore strata of the Wolfville Formation and have recovered numerous important new vertebrate fossils.
Both the published literature and media releases contain many erroneous statements concerning the early Mesozoic continental biotas from the Fundy region; often such statements have been based on cursory examination of unprepared material. This problem, combined with the broader significance of the tetrapod fossils of the Fundy basin--particularly for understanding the end-Triassic mass extinction (ETE)--has provided the impetus for the present review.
Overall geological context
The Fundy basin is the largest of the exposed rift basins in eastern North America, which together comprise the western part of the conjugate-margin rift system that formed during the Late Permian to Jurassic continental rifting phase of the breakup of Pangaea (Olsen et al. 2000, 2003a, b, 2005a, b; Olsen and Et-Touhami 2008; Fig. 1). The igneous and sedimentary fill of these rift basins represents the Newark Supergroup (Olsen 1978). Continental rifting probably commenced in eastern North America during the Permian, as documented by deposits in New Brunswick described below. It terminated in the Early Jurassic, within a few million years of the major tectonic paroxysm at the end of the Triassic that resulted in the emplacement of basaltic intrusions and extrusions of the Central Atlantic Magmatic Province (CAMP) (Marzoli et al. 1999; Olsen et al. 2003a; Blackburn et al. 2013), which is Earth's geographically most extensive flood-basalt province. The emplacement of CAMP is temporally, and possibly causally, related to the end Triassic extinction.
Structurally, the Fundy basin is a faulted and eroded half-graben, situated on the suture between the Avalon and Meguma terranes (Wade et al. 1996), both of which were accreted to the future North America during the Palaeozoic. It is bounded by the largely normal Fundy fault and Grand Manan fault systems on its northwestern and western sides and the transtensional Cobequid-Chedabucto (or Minas) fault system to the north (Fig. 2). All these systems are reactivated Palaeozoic fault zones (Withjack et al. 1995; McHone 2011). The southern and southeastern margins of the basin are marked by onlap onto hanging-wall rocks of the Meguma terrane and overlying late Palaeozoic strata. The Fundy basin occupies an area about 16 500 [km.sup.2] and is largely covered today by the Bay of Fundy and its inner eastern arm, the Minas Basin. However, extensive outcrops of the basin deposits occur along the shores of west-central Nova Scotia and, to a much lesser extent, on the southeastern shores of New Brunswick. A thickness of at least 4 km of sedimentary and volcanic rocks is preserved in the deepest parts of the basin along the Fundy and Grand Manan fault zones based on industry seismic lines (Wade et al. 1996; McHone 2011). However, the entire section thins dramatically to the east and south towards the outcrops in Nova Scotia by convergence, onlap, non-deposition and erosion. Similarly, the sections of erosional remnants outcropping in New Brunswick, on the Fundy fault zone on footwall rider blocks, are either much thicker than correlative units on the hanging wall, or represent units unknown on the hanging wall. Along with the divergence of strata towards the Fundy and Grand Manan fault zones revealed by seismic profiles, two deep exploratory drill holes in the Bay of Fundy, and several much shallower cores on the Nova Scotian outcrop belt, the outcrops reflect the growth of the sedimentary basin during at least the early Mesozoic extension along the Fundy and Grand Manan fault zones (Withjack et al. 1995). At the same time much more complex syntectonic basin geometries developed along the transtensional Cobequid-Chedabucto fault system (Olsen et al. 1990).
A major outlier of early Mesozoic rocks crops out on the shores of Grand Manan Island, New Brunswick. McHone (2011) considered it a separate basin, and thus it will not be discussed further in the present paper.
Stratigraphy and age of the Fundy basin
Powers (1915, 1916) established an outline of the stratigraphy of the Fundy basin (Fig. 3) based on extensive fieldwork and review of older literature. He recognized three stratigraphic units:
(1) the basal Annapolis formation, divided informally into a lower, brown and red Wolfville sandstone and an upper, mostly red Blomidon shale; these two units were supposedly separated locally by the Five Islands volcanics;
(2) the lava flows of the North Mountain Basalt;
(3) the largely white and green cherty limestones of the Scots Bay Formation.
Klein (1960, 1962) abandoned the term Annapolis formation and established the Wolfville and Blomidon formations for Powers' lower and upper units, respectively. He used the term McKay Head Basalt for the basalt flows and volcanoclastics included by Powers in the supposedly intervening Five Islands volcanics. Klein also included all sedimentary and volcanic rocks of the Fundy basin in the Fundy Group.
Olsen (1978) raised the rank of the Newark Group of Redfield (1856) to Newark Supergroup, to encompass all early Mesozoic rocks of eastern North America, and thus including the Fundy Group. We chose not to apply the group nomenclature of Weems and Olsen (1997) in which the Fundy basin sequence is divided into a lower Chatham Group and an upper Meriden Group, both of which extend across eastern North America, because it requires an explicitly chronostratigraphic, as opposed to lithostratigraphic framework, and the interpreted regional similarities are conceptually better handled within a tectonostratigraphic framework (Olsen 1997).
Liew (1976) posited that the strata above the Five Islands volcanics of Powers (1916) were equivalent to the Scots Bay Formation. Using a combined biostratigraphic and facies argument, Olsen (1981) argued that the McKay Basalt and the Five Islands volcanics represent the same set of lava flows as the North Mountain Basalt, concurring with Liew. This interpretation has generally been followed (Stevens 1980, 1987; Williams et al. 1985; Tanner 1996), and the thick, mostly red sedimentary unit above the North Mountain Basalt was informally designated as the McCoy Brook formation on maps and in guidebooks (Donohoe and Wallace 1978, 1982: Keppie 1979: Olsen et al. 1989). Tanner (1996) formalized the McCoy Brook Formation, provided a type section (adjacent to McCoy Brook at McKay Head), and reclassified the Scots Bay Formation as a member of the McCoy Brook Formation.
Outliers of the Fundy Group occur along the Fundy coast of New Brunswick. As summarized by Luttrell (1989), these strata have a complex nomenclatural history, beginning with Powers (1916). We argue that, with two exceptions (Honeycomb Point and Lepreau formations), these units should be recognized as members of the Wolf-ville Formation (Figs. 3-5; Appendix). These units have yielded sparse and as yet poorly studied but potentially important faunal and floral assemblages.
Olsen et al. (2000) introduced informal names for palaeontologically important members of the Wolfville and Blomidon formations (Fig. 3). Here we formalize these units and provide type sections and brief descriptions (Appendix; Fig. 3). In ascending order, the formally defined units are the Economy and Evangeline members of the Wolfville Formation and the Red Head, White Water, and Partridge Island members of the Blomidon Formation.
The formations of the Fundy basin can be grouped into four tectonostratigraphic sequences (TS I to TS IV; Figs. 5-6), most of which are bounded by unconformities (Olsen 1997) and are thus sequences in the sense of sequence stratigraphy (Christie-Blick and Driscoll 1995). The sequences probably resulted from significant changes in the rate of extension, as opposed to changes in sea level (Olsen 1997). The oldest of these sequences, TS I, is represented by the Honeycomb Point Formation and possibly the Lepreau Formation, and is characterized by fluvial and aeolian strata of Late Permian age (Olsen et al. 2005a, b; see below). The Quaco Member of the Wolfville Formation unconformably overlies the Honeycomb Point Formation. The Wolfville Formation comprises TS II, of possibly Middle to early Late Triassic (Carnian) age based on biostratigraphy (see below), and consists of aeolian, fluvial and possibly lacustrine strata that seem to have been, on the whole, deposited under a more humid climatic regime than strata of TS I. At least locally, TS II is unconformably overlain by TS III, which comprises almost the entire Blomidon Formation. TS III was deposited under relatively arid climatic conditions and is of Norian and Rhaetian age. Its age is constrained by palaeo-magnetic correlation to the Newark basin astrochronology and marine sequences (Kent and Olsen 1999; Muttoni et al. 2004; Olsen et al. 2011). TS IV conformably overlies TS III and consists of the late Rhaetian top member of the Blomidon Formation and (overlying the North Mountain Basalt) the McCoy Brook Formation, which is of latest Rhaetian to Hettangian (and possibly younger) age. The dating of the uppermost Blomidon Formation is based on biostratigraphy and palaeomagnetic polarity stratigraphy, whereas the North Mountain Basalt has yielded a series of increasingly more precise zircon [sup.206.Pb]/[sup.238.U] dates (Schoene et al. 2006, 2010) culminating with a chemical abrasion TIMS single-crystal U-Pb date of 201.566 [+ or -] 0.031 Ma (Blackburn et al. 2013). These latest dates are in addition to older K-Ar and 40Ar/39Ar (Carmichael and Palmer 1968; Armstrong and Besancon 1970; Hayatsu 1979) and zircon U-Pb (Hodych and Dunning 1992) dates. The age of the McCoy Brook Formation is constrained by that of the underlying North Mountain Basalt and by biostratigraphy (see below).
FOSSIL ASSEMBLAGES: VERTEBRATE DIVERSITY AND BIOSTRATIGRAPHIC SIGNIFICANCE
Tectonostratigraphic Sequence I: Honeycomb Point and Lepreau formations
The oldest unit of the Fundy Group, the Honeycomb Point Formation, outcrops in the vicinity of St. Martins, New Brunswick, and is the only part of the Group that definitively represents TS I (Fig. 5). To date, the Honeycomb Point Formation has yielded only silicified wood (Powers 1916), trace fossils and possible scraps of bone.
The first-recorded occurrence of tetrapod ichnofossils from the Honeycomb Point Formation is in Baird's field notes for 1959 (Baird MS, pp. 271, 276), in which he mentions footprints in the roof and on the base of the 'caves' at Macs Beach, St. Martins, New Brunswick (45.357467[degrees]N, 65.523531[degrees]W). William Take apparently first discovered some of these tracks. PEO also saw one example on the roof of the westernmost cave on a field trip with Baird in 1973 (Baird MS, p. 540), consisting of curved scratch marks in positive hyporelief. Unfortunately, there appear to be no photographic or other records of these occurrences, and PEO has not seen any tetrapod traces at this locality since that time.
Outcrops of Honeycomb Point Formation both east and west of Honeycomb Point proper have yielded a few tetrapod tracks (Olsen and Et-Touhami 2008; Fig. 7). These do not resemble any similar-sized ichnites from the other basins of the Newark Supergroup but are similar to Permian tetrapod ichnotaxa such as Dimetropus or Hyloidichnus in being markedly asymmetrical, with medially curved and expanded distal digit imprints. However, the Honeycomb Point tracks are not sufficiently well preserved for confident assignment to any particular ichnotaxon. Furthermore, these tracks are either not readily accessible or cannot be collected, being high on a cliff face in one case or on the underside of a very large boulder in another. Olsen and Et-Touhami (2008, fig. 21) published a measured section with these occurrences.
The only possible tetrapod skeletal remains from the Honeycomb Point Formation are apparently unidentifiable fragments of bone that Baird recorded from the north side of Quaco Head in conglomerate and arkose in 1959 (Baird MS, p. 271). These finds were housed at the NSM in 1959, but their current repository is unknown. It is also uncertain whether these remains did in fact derive from the Honeycomb Formation because Carboniferous conglomerate and arkose also crop out at Quaco Head.
Based on published biostratigraphic information, the age of the Honeycomb Point Formation is uncertain. Olsen and Et-Touhami (2008) argued that this formation is Late Permian in age based on facies similarity to the Cap Aux Meules Formation of the Magdalen basin in the Gulf of St. Lawrence. The latter unit is constrained in age by unconformably overlying strata of Early Permian (Sakmarian) age and having a Permian pole position (Tanczyk 1988). Palaeomagnetic data from the Honeycomb Formation indicate largely reverse polarities, with higher strata being of mixed polarity; this is consistent with a Late Permian age (Olsen et al. 2000, 2002), but the details remain unpublished. The upper limit of the age of the Honeycomb Point Formation is based on palynological samples recovered from the unconformably overlying Wolfville Formation (formerly Echo Cove Formation) that indicate an early Late Triassic (Carnian) age. Finally, the tectonostratigraphcally homotaxial Ikakern Formation in Morocco is unquestionably Permian in age based on its vertebrate fossils and other biostratigraphic evidence (Jalil 1999; Jalil and Janvier 2005; Voigt et al. 2010) and can be correlated with the Honeycomb Point Formation based on preliminary palaeomagnetic polarity stratigraphy and pole positions (Olsen et al. 2002a).
The more than 2000 m thick Lepreau Formation (Fig. 2A), which crops out in an outlier at Lepreau, southwest of Saint John, New Brunswick, is of uncertain age. From an isolated outcrop at Lepreau Falls on the Lepreau River, Sarjeant and Stringer (1978) reported a small tetrapod trackway and referred it to the ichnotaxon Isocampe from the Hartford basin. Sarjeant and Stringer assigned the strata hosting the trackway to the Lepreau Formation and, based on their identification of Isocampe, dated them as Triassic. However, the trackway shows characters diagnostic only at the level of Tetrapoda and thus is not biostratigraphically useful. Subsequently, the strata at Lepreau Falls have been recognized as part of the Carboniferous Balls Lake Formation (McLeod and Johnson 1998; MacNaughton and Pickerill 2010). The main outcrop of the Lepreau Formation is of uncertain age, and no skeletal remains or tetrapod tracks have been reported from it.
Tectonostratigraphic Sequence II: Wolfville Formation
The Wolfville Formation represents TS II in the Fundy basin, and in it we group not only the Wolfville Formation sensu Klein (1962) but also the Quaco Formation (Powers 1916; Nadon and Middleton 1985) and Echo Cove Formation (Nadon and Middleton 1985) (Fig. 3). To date no tetrapod fossils have been reported from the Wolfville Formation of New Brunswick, and thus we will restrict our discussion primarily to exposures in Nova Scotia, from which two distinct tetrapod assemblages have been identified: a stratigraphically older assemblage from the Economy Member and a younger one from the Evangeline Member (Fig. 5).
Strata of the Economy Member (defined in Appendix; Fig. 4G) consist largely of fluvial deposits interbedded with a few significant intervals of aeolian sandstone, which are generally absent in the rest of the Wolfville Formation. The type area at Lower Economy in Colchester County is in a structurally isolated block on the northern side of the Minas Basin. A very similar sequence, including aeolian strata, on the southern shore of the Minas Basin (Leleu et al. 2010) that we place in the Economy Member, is overlain by the middle Wolfville Formation (Evangeline Member) (see Appendix).
Starting in 1966, Donald Baird and his teams prospected coastal exposures of the Economy Member in the Lower Economy area (Fig. 8), recovering dissociated bones and teeth representing a considerable diversity of tetrapods. More recently PEO, T im Fedak (Fundy Geological Museum) and others have collected additional vertebrate fossils from this section. Unfortunately, most specimens are too fragmentary to permit lower-level taxonomic identification and often even basic anatomical assessment. However, enough material has now been identified to establish that this tetrapod assemblage is distinct from other, younger assemblages in the Newark Supergroup and elsewhere.
Bones occur mostly as isolated clasts in fluvial, calcitecemented intraformational conglomerate and lithicclast, pebbly intraformational conglomerate, along with occasional unionoid bivalves (Fig. 8B). These deposits form dune-scale trough cross-beds.
Temnospondyl stem-amphibians from the Economy Member are referable to two groups, Capitosauroidea and Trematosauroidea, distinguishable on the basis of jaw fragments. The symphyseal portion of a large capitosauroid mandible (FGM998GF8) has a blunt anterior margin and a pair of tusks, followed behind by a row of smaller postsymphyseal teeth (Fig. 9A). The latter feature argues against referral of this jaw fragment to Mastodonsauridae, but it is present in certain other capitosauroids such as Parotosuchus (Schoch and Milner 2000). Additional capitosauroid remains include mandibular fragments (e.g., YPM VPPU 021692; Fig. 9B) and a small piece of the left postorbital region of a skull roof (YPM VPPU 023501).
Welles (1993) referred the trematosauroid cranial remains to the slender-snouted lonchorhynchine Cosgriffius, which was first reported from the Wupatki Member of the Moenkopi Formation (of Olenekian age) in Arizona. The remains reported by Welles include an incomplete left mandibular ramus with 78 preserved tooth positions, many of them still with partial tooth crowns (YPM VPPU 021691) (Fig. 9C). There are no diagnostic features to suggest that the material from the Economy Member is referable to Cosgriffius (as proposed by Welles) rather than another lonchorhynchine taxon. A fragment identified by Welles (1993) as a left premaxilla (YPM VPPU 023686) is not clearly identifiable as such. The posterior region of a left mandibular ramus (YPM VPPU 021692) assigned to Cosgriffius by Welles (1993) belongs to a capitosauroid based on the long, transversely broad and concave postglenoid region, the shape of its posterior end, and the ornamentation on its lateral surface (Fig. 9C).
Complete or partial jaws with teeth, as well as a few other bones, document the presence of procolophonid parareptiles. The smallest dentaries hold a few simple conical teeth (e.g., NSM012GF032.007), whereas larger ones (e.g., FGM000GF86) have transversely broad, bicuspid teeth more posteriorly. It is not clear whether this difference indicates the presence of multiple taxa or merely different growth stages of a single form. Li (1983) documented ontogenetic change from conical, sometimes labiolingually compressed tooth crowns to transversely wide bicuspid crowns in the Early Triassic procolophonid Eumetabolodon brachycephalus from Inner Mongolia, China. The neural arch of a dorsal vertebra (YPM VPPU 023500; width across prezygapophyses: 40 mm) probably belongs to a rather large procolophonid based on its 'swollen' configuration.
Archosauromorph reptiles are represented by at least four groups. An incomplete cervical vertebra (YPM VPPU 022000) represents the first record of a long-necked tanystropheid from North America (Fig. 10). It most closely resembles anterior to mid-cervical vertebrae of Tanystropheus spp. from the Anisian to Norian of Europe, the Anisian of the Middle East, and the Ladinian or Carnian of China (Wild 1973, 1980; Rieppel et al. 2010). The neural spine forms a low dorsal ridge, and the postzygapophyses extend posteriorly beyond the posterior end of the centrum. The vertebral centrum is distinctly elongated (length: 76 mm, anterior height: c. 7 mm), more so than in more basal tanystropheid taxa (Sennikov 2011), and we thus identify it as cf. Tanystropheus sp.
An isolated tooth crown (NSM012GF032.001) is labiolingually wide (c. 7 mm) and has three distinct cusps (with worn or abraded apices) that are linked by low ridges. As preserved, the central cusp is the smallest and one of the outer cusps is larger than the other two cusps. The tooth is proportionally narrower transversely than teeth of the archosauromorph Trilophosaurus (Spielmann et al. 2008) and most closely resembles teeth of the enigmatic Tricuspisaurus thomasi from Late Triassic (Norian) fissure fillings in Wales. The latter taxon has variously been classified as a trilophosaurid (Robinson 1957) or a procolophonid (Fraser 1985).
A well-preserved left pubis with an attached fragment of the ilium (YPM VPPU 021806) has a distinct pubic 'apron' and most likely represents an archosauriform. A partial left mandibular ramus of a small reptile with nine preserved alveoli and teeth (NSM012GF032.002; preserved length: 32 mm) is possibly referable to the Archosauriformes based on the distinctive ornamentation of fine ridges and grooves along the ventrolateral surface of the dentary. The dentary is long and low, and its medial surface is concealed by the splenial, which is separated from the dentary by a long, slender coronoid more posteriorly. A similarly long and splint-like coronoid is present in various archosauriform reptiles, but also in the crocodylomorph Sphenosuchus (Gower 2003). The small teeth have simple conical crowns and show thecodont implantation. There are two possibly pathological swellings on the dorsolateral margin of the jaw behind the tooth row and on the ventromedial edge further posteriorly, respectively.
Finally, tall, slender and apically recurved tooth crowns with serrated cutting edges (e.g., YPM VPPU 019909; 4 serrations per mm) presumably have archosauriform affinities but cannot be assigned to a particular taxon.
Huber et al. (1993) established the Economian Land Vertebrate Faunachron based on the tetrapod remains from the Economy Member of the Wolfville Formation and considered it Anisian in age. The currently available tetrapod material from the Economy Member, however, is inadequate for a definitive biochronological assessment on its own. Huber et al. (1993) highlighted the presence of what they called cf. Cosgriffius sp. because Cosgriffius campi occurs in the Wupatki Member of the Moenkopi Formation in Arizona (Welles 1993), which has been dated as late Early Triassic (Olenekian) by Lucas and Schoch (2002). Previously reported lonchorhynchine trematosaurids all date from the Early and early Middle Triassic, but two clades of Trematosauridae are now known to range into the Late Triassic (Schoch and Milner 2000; Sues and Schoch 2013). Thus, it is conceivable that the lonchorhynchine from the Economy Member, which is not definitely referable to Cosgriffius, is geologically younger. Tanystropheus has a reported stratigraphic range extending from the late Anisian to the late Norian in Europe (Wild 1980). None of the identifiable tetrapod taxa from the Economy Member has been recorded from the overlying Evangeline Member of the Wolfville Formation, which has yielded at least one taxon (Metoposaurus bakeri) indicating a Carnian age (see below).
Whereas all the identifiable tetrapod taxa from the Economy Member have long ranges that are not diagnostic at the level of age (stage) or even epoch, a sequence of members comparable to that of the Wolfville Formation occurs in the Timezgadiouine Formation of the Argana Basin in the western High Atlas of Morocco, which was deposited at a tropical palaeolatitude similar to that of the Wolfville Formation (Olsen and Et-Touhami 2008). There, the lower part of the Timezgadiouine Formation, the Aglegal Member, has yielded capitosauroids but lacks metoposaurs and is succeeded by the Irohalene Member with abundant metoposaurs and no capitosauroids (Jalil 1999). The Aglegal Member has also yielded unambiguous examples of the pseudosuchian ichnotaxon Chirotherium barthii, which is restricted to Middle Triassic strata elsewhere (Klein et al. 2011). This suggests that the partitioning of the temnospondyl assemblages into an older capitosauroid-trematosaurid and a younger metoposaurid assemblage has temporal significance within the Pangaean tropics, corresponding in a broad way to the similar partitioning of the Early to Middle Triassic temnospondyl assemblages from the Moenkopi Formation and the Late Triassic ones from the Chinle Formation, which were also deposited at tropical palaeolatitudes. However, no such temporal partitioning is evident in the higher-latitude Germanic Basin tetrapod assemblages where capitosauroids have a range apparently spanning the entire Triassic Period (Schoch and Milner 2000; Schoch 2011).
The upper part of TS II is made up of the Evangeline Member, the type section of which consists of the coastal outcrops at Evangeline Beach, Kings County (defined in Appendix; Fig. 4E-F). Skeletal remains of tetrapods are quite common in this member, not only as dissociated bones and skulls in the calcite-cemented, pebbly intra-formational conglomerate beds as in the Economy Member (found along with unionoid clams) but also as bones and skeletons in the better-sorted sandstones and mudstones. The most important sections for tetrapod fossils in the Evangeline Member are the type section, Burntcoat Head (Burntcoat, Hants County) and near the community of Noel Shore (Hants County) (Fig. 11). Other less productive sites for skeletal remains include Boot Island (Kings County) and Longspell Point (Kingsport, Kings County).
William Take first discovered tetrapod bones in the Evangeline Member and brought them to the attention of Donald Baird in November 1958. At first in collaboration with Take (Baird and Take 1959), Baird undertook subsequent palaeontological reconnaissance of the strata of this unit. After 1985 the present authors and others have continued this work.
Although scraps of bone are not uncommon, the dissociated and fragmentary nature of most skeletal remains often renders their anatomical and taxonomic identification difficult, and sometimes impossible. It was only through persistent collecting over more than four decades that sufficient material has been gathered to permit a new scientific evaluation of the tetrapod assemblage from the Evangeline Member. Very rarely, partial tetrapod skeletons and associated but disarticulated bones of tetrapods occur both in sandstones and mudstones. We offer here what is perhaps a conservative assessment of the tetrapod biodiversity in the Evangeline Member, based only on specimens that show derived features diagnostic for particular clades.
To date, temnospondyls are represented only by the metoposaurid Metoposaurus bakeri (originally assigned to "Buettneria" by Case 1931). It occurs as a natural mould of much of a skull roof from Noel Head (YPM VPPU 021742; Baird 1986; Hunt 1993) (Fig. 12). As in specimens of Metoposaurus bakeri from Texas, the elongate lacrimal is excluded from the anterior margin of the orbit by the contact between the prefrontal and jugal (Hunt 1993; Sulej 2007). YPM VPPU 021742 represents an immature specimen based on its small size (length of skull roof along the midline c. 190 mm), as well as the relative proportions and pattern of sculpturing of the skull roof, especially in the postorbital region. In addition to this skull roof, the mould of a clavicle with characteristic external sculpturing and isolated vertebral centra provide evidence for the presence of metoposaurid temnospondyls in the Evangeline Member. Metoposaurids have long, dorsoventrally strongly flattened skulls and small orbits that are placed far forward on the cranium. These animals were obligatory aquatic predators. Despite reviews by Hunt (1993) and Sulej (2007), a rigorous phylogenetic assessment of metoposaurid diversity is still needed. For example, Baird (1986), Hunt (1993) and Schoch and Milner (2000) assigned the species bakeri to Metoposaurus, whereas Sulej (2007) still followed Case (1931) in retaining this taxon in "Buettneria" (a preoccupied generic name now replaced by Koskinonodon; Mueller 2007).
By far the most common tetrapod fossils in strata of the Evangeline Member are tooth-bearing jaws of procolophonid parareptiles (Fig. 13). Sues and Baird (1998) formally named and described three taxa diagnosed by their respective dentitions: Acadiella psalidodon, Haligonia bolodon, and Scoloparia glyphanodon. They also re-identified a skull and associated postcranial bones (NSM996GF82.1), earlier referred by Baird and Olsen (1983) to Leptopleuron, which is otherwise known only from the Lossiemouth Sandstone Formation (Late Triassic) of Scotland (Saila 2010), as an immature specimen of Scoloparia glyphanodon.
Scoloparia glyphanodon is by far the most common procolophonid in the Evangeline Member (Fig. 13A). In addition to numerous jaw elements, it is known from several skulls. The more posterior maxillary and dentary teeth of Scoloparia have transversely aligned, chisel-like tooth crowns that bear three cusps when unworn rather than only two as in most procolophonids. The quadratojugal bears a cluster of long, slender, posterolaterally projecting bony spines. The holotype of Scoloparia glyphanodon (NSM996GF83.1) has a 'nuchal shield' composed of small, polygonal osteoderms, but no other known specimen preserves this distinctive feature (Sues and Baird 1998). Phylogenetic analysis places Scoloparia as a member of Leptopleuroninae, the most derived clade of Procolophonidae, which also includes the Late Triassic (Norian-Rhaetian) Hypsognathus fenneri from eastern North America (Sues et al. 2000). Cisneros (2008) placed Scoloparia glyphanodon as the sister-taxon of the Early to early Middle Triassic Sclerosaurus armatus from the Buntsandstein of Germany and Switzerland based solely on the shared presence of dermal armour. However, this coding ignores the profound differences in the structure of the dermal armour in the two taxa. Unlike Scoloparia, Sclerosaurus has two or three rows of sculptured osteoderms on either side of the midline of the body and lacks a 'nuchal shield' (Sues and Reisz 2008).
The holotype of Acadiella psalidodon comprises an associated right maxilla and partial mandibular ramus as well as part of the pterygoid flange (NSM996GF69.1; Fig. 13B). Its posterior maxillary and dentary teeth have anteroposteriorly rather than transversely aligned crowns with serrated apical ridges (Sues and Baird 1998). Haligonia bolodon, known only from a right maxilla (NSM996GF74.1, holotype) and a left dentary (NSM996GF31.1), has upper and lower tooth rows that have four small teeth followed by a greatly enlarged tooth with a bulbous crown at the back of the jaw. As yet too little is known about the cranial structure of Acadiella psalidodon and Haligonia bolodon to assess their respective phylogenetic positions. Procolophonid parareptiles are superficially lizard-like forms usually less than 50 cm long. Their structure of their dentition suggests herbivorous or omnivorous habits.
Archosauromorph reptiles are represented in the Evangeline Member by a rhynchosaur, a trilophosaur, diverse pseudosuchians, and a possible ornithodiran (Figs. 14-16).
Baird (in Carroll et al. 1972) reported the presence of two taxa referable to a group of probably herbivorous archosauromorph reptiles, Trilophosauridae. These identifications were based on fragmentary cranial remains and thus are problematical. One of these specimens, a natural mould of a small dentary, is referable to Teraterpeton hrynewichorum, which Sues (2003) named on the basis of an excellently preserved, nearly complete skull and much of the postcranial skeleton collected from Burntcoat Head by the avocational collectors George and Sandy Hrynewich (NSM994GF041; Fig. 14A). As in the Late Triassic Trilophosaurus spp. from the American Southwest (Spielmann et al. 2008), the skull of Teraterpeton hrynewichorum has only large upper temporal fenestrae and an otherwise solid, deep temporal region. Unlike in Trilophosaurus spp., the edentulous premaxillae and symphyseal portions of the dentaries are elongate. The external naris is distinctly longer than the orbit. Both the maxilla and palatine bear teeth whose crowns have bulbous bases, a single tall cusp, and an anterior (mesial) 'heel' whereas the dentary teeth have the reverse configuration with a tall cusp and a posterior (distal) 'heel' Phylogenetic analysis indicated that Teraterpeton hrynewichorum is most closely related to Trilophosaurus spp. among known archosauromorph taxa (Sues 2003). Like rhynchosaurs, Teraterpeton was presumably herbivorous. The distinctive structure of its jaw joint and its maxillary and palatine teeth indicate fore-and-aft jaw motion of the mandible. The deep, blade-like ungual phalanges and robust pectoral girdle suggest that Teraterpeton hrynewichorum was a burrower (which may well account for the excellent, articulated preservation of the holotype).
Jaw elements of various sizes (Fig. 14B-C), incomplete fused parietals (NSM012GF032.023), and the excellently preserved basicranial portion of a braincase (NSM012GF032.022; Fig. 14D) document the presence of a hyperodapedontine rhynchosaur in the Evangeline Member (Baird 1963). Skeletal remains of this taxon have most frequently been found at Evangeline Beach. As in other rhynchosaurs, the premaxilla (NSM012GF032.024) is downturned (relative to the maxilla) and forms an edentulous 'beak' (Fig. 14B). The maxilla has only a single deep longitudinal occlusal groove separating the lateral and medial rows of teeth (1 or 2 each) (Fig. 14C). The lateral teeth are pyramidal. Baird (in Carroll et al. 1972) compared the material to the Hyperodapedon gordoni from the Lossiemouth Sandstone Formation of Scotland. Later authors (e.g., Lucas et al. 2002) referred the Wolfville material to the genus Hyperodapedon without further discussion. The rhynchosaur from the Evangeline Member is distinguished from most other hyperodapedontines by the absence of lingual teeth on the dentary. During the
Triassic, rhynchosaurs were a widely distributed group of presumably herbivorous archosauromorph reptiles. The maxillae typically bear multiple rows of teeth on either side of a longitudinal groove; some derived taxa have additional grooves between the tooth rows.
Archosaurian reptiles from the Evangeline Member comprise various taxa of crocodile-line archosaurs (Pseudosuchia) (Figs. 15, 16A-B) and a possible representative of bird-line archosaurs (Ornithodira) (Fig. 16C). Several isolated osteoderms with a raised anterior 'bar' and radiating ornamentation are typical of Aetosauria, a group of heavily armoured, omnivorous or herbivorous pseudosuchians from the Late Triassic. A paramedian dorsal osteoderm of an aetosaurine (NSM012GF032.033; Fig. 15D; greatest width: 59 mm) shows distinct flexure along the midline and well-developed sculpturing composed of closely spaced pits, the more anterior ones of which are elongate and extend anterolaterally. A ventral osteoderm (NSM012GF032.032; Fig. 15E; greatest width: 24 mm) has relatively weak, sparse pitting and resembles those of Coahomasuchus kahleorum from the Dockum Group (Late Triassic) of Texas (William Parker, personal communication). The well-preserved proximal portion of a right femur (NSM012GF032.014; Fig. 15B) is referable to aetosaurs based on the large posteromedial tuber on the proximal end and the structure of the fourth trochanter (Nesbitt 2011). Scattered postcranial remains recovered from a mudstone horizon at Burntcoat probably belong to a small aetosaur. The rectangular osteoderms bear sculpturing composed of minute pits.
Mostly incomplete and dissociated skeletal elements document the presence of paracrocodylomorph pseudosuchians (Figs. 15, 16A-B). A set of articulated posterior cervical and anterior dorsal vertebrae with associated ribs (NSM998GF46.1; Fig. 15A) probably belongs to a paracrocodylomorph. The vertebrae have tall neural spines. A left tibia (NSM012GF032.015; Fig. 15C; length: 131 mm) has a straight shaft and is gently concave posteriorly at its distal articular end. It is probably referable to a paracrocodylomorph. A well-preserved partial braincase (yPM VPPU 020750; Fig. 16A-B) closely resembles that of Postosuchus kirkpatricki from Late Triassic strata in the American Southwest (Weinbaum 2011, fig. 24), especially in the structure of the parabasisphenoid, which is greatly elongated between the basal tubera and has a deep, dorsoventrally extended median recess. However, the parabasisphenoid is less extended vertically, and the prootic has separate foramina for branches V1 and V2-3 of the trigeminal nerve (Fig. 16A).
Surprisingly, the Evangeline Member has not yielded any diagnostic remains of phytosaurs to date. These superficially crocodile-like amphibious predators are very common in other Late Triassic deposits in Europe, Morocco, and North America and are typically found in association with the perennially aquatic metoposaurs. Phytosaurs were long considered early crocodile-line archosaurs but Nesbitt (2011) recently placed them outside crown-group Archosauria.
In contrast to crocodile-line archosaurs, bird-like archosaurs (Ornithodira) are very rare in the Evangeline Member. Baird (in Carroll et al. 1972) reported the presence of dinosaurs in this unit. He identified recurved, labiolingually flattened tooth crowns with finely serrated mesial and distal cutting edges as representing three size classes of theropod dinosaurs. The largest tooth crown in our sample has a mesiodistal diameter of 23 mm near the base and carinae with 5 serrations per millimetre. There are no features to suggest that any of these teeth are dinosaurian or even ornithodiran, and at least some of them more likely belong to paracrocodylomorph pseudosuchians.
Baird (in Carroll et al. 1972) reported a partial left maxilla containing a single tooth (NSM004GF012.001) as representing a tiny ornithischian dinosaur. Irmis et al. (2007, fig. 5B-D) published drawings of the jaw fragment (made by PEO) and showed that it lacks any features exclusive to ornithischians. Instead they noted similarities to Revueltosaurus callenderi, which was initially known only from isolated teeth from the Bull Canyon Formation (Late Triassic: Norian) of New Mexico that were considered ornithischian in origin. Recent finds of extensive skeletal remains of Revueltosaurus callenderi from the Chinle Formation (Late Triassic: Norian) of Arizona have now established that this taxon is a pseudosuchian closely related to aetosaurs, not an ornithischian dinosaur (Parker et al. 2005; Nesbitt 2011). A well-preserved left ilium lacking only the postacetabular process (NSM012GF032.021) from Evangeline Beach closely resembles those of aetosaurs but is also similar to that of Revueltosaurus (Parker et al. 2005, fig. 3c) in its possession of a short anterior (preacetabular) process.
To date the only possibly ornithodiran discovery from the Evangeline Member is a specimen comprising an articulated set of incomplete right metatarsals II--IV, each associated with the proximal phalanx of its respective pedal digit (YPM VPPU 021694); this specimen is preserved in part as bone and in part as natural mould that was filled in with plaster to document its former structure (Fig. 16C). On the associated label Baird identified this find as belonging to a small theropod dinosaur. However, there are no diagnostic features to indicate dinosaurian affinities. The metatarsals are long, slender, and appressed for their entire preserved lengths. Although some early crocodylomorphs also have such 'bundling' of the metatarsals these elements are generally not appressed for their entire length (Nesbitt 2011), and thus YPM VPPU 021694 more likely represents an ornithodiran.
Non-mammalian synapsids (therapsids) are represented only by the large traversodontid cynodont Arctotraversodon plemmyridon (Hopson 1984; Sues et al. 1992) and the as-yet-undescribed pelvic bones of a large dicynodont (Tim Fedak, personal communication). Arctotraversodon plemmyridon is known from three partial dentaries and three isolated teeth. The holotype of this taxon (YPM VPPU 019190; Fig. 17) is an incomplete right dentary (with an attached fragment of the left one) from the northeast corner of the Burntcoat headland. Arctotraversodon is readily distinguished by procumbent incisors with coarsely serrated mesial and distal cutting edges (Fig. 17A) and the presence of an enlarged mental foramen on the buccal surface of the dentary (Fig. 17B). Referred molariform postcanine teeth have mesiodistally short tooth crowns (Sues et al. 1992). An isolated lower postcanine (NSM983GF2.1) has three rather than two anterior cusps, a derived feature shared with Boreogomphodon jeffersoni from Late Triassic (Carnian) strata in Virginia and North Carolina, which also shares the presence of an enlarged mental foramen on the buccal surface of the dentary (Sues and Hopson 2010). Baird and Olsen's (1983) report of a dicynodont therapsid was based on the partial braincase (YPM VPPU 020750) reidentified here as that of a paracrocodylomorph pseudosuchian. However, Tim Fedak (personal communication) has found the ilia and sacrum of a large dicynodont, but this material has not yet been fully prepared and studied.
With the exception of Metoposaurus bakeri, all tetrapod remains from the Evangeline Member that are identifiable at lower taxonomic levels to date appear to be restricted to this unit and thus have no biostratigraphic utility. Metoposaurus bakeri itself is a faunal element of the Otischalkian, the oldest of the Late Triassic Land Vertebrate Faunachrons defined by Lucas (1998) in the American Southwest, and the only taxon that may be Carnian rather than Norian in age. Kozur and Weems (2010) reported the presence of a monospecific conchostracan assemblage with Euestheria minuta from Evangeline Beach (based on material collected by PEO). They argued that this species is restricted to what they considered early Carnian (Cordevolian) strata in the more southeastern basins of the Newark Supergroup. Presumably this is the same taxon that Powers (1916) reported as Estheria ovata from the Evangeline Member of Long Island (Evangeline Beach; Baird in Carroll et al. 1972) and Boot Island. Based on these faunal elements alone, a more precise dating than late Middle to early Late Triassic is not possible. However, the position of the Evangeline Member assemblage in the lower part of the basin section, well below strata dated as Norian based on magnetostratigraphy (see below), and below the position of the boundary between TS II and TS III, suggests a Carnian age.
Whiteside et al. (2011) argued that the procolophoniddominated Late Triassic tetrapod assemblages from the Newark Supergroup existed under semi-arid climatic conditions, whereas more or less coeval communities dominated by traversodontid cynodonts from Virginia and North Carolina appear to have been restricted to a narrow equatorial zone with more humid conditions. The tetrapod assemblage from the Evangeline Member clearly falls into the former category, with procolophonids representing most of the identifiable fossils. The traversodontid cynodont Arctotraversodon plemmyridon is only known from a few specimens, unlike its close relative Boreogomphodon jeffersoni, which tends to be common where present. Whereas the presence of relatively large, thick-shelled unionoid clams argues for perennial river settings, the presence of abundant palaeosol rhizoliths suggests at least seasonally dry conditions. The relative scarcity of metoposaurs and apparent absence of phytosaurs are consistent with the latter interpretation.
The stratigraphically highest outcrops of the Evangeline Member that have yielded bone are at Longspell Point near Kingsport, Kings County (e.g., Baird MS, p. 253); this occurrence is in calcite-cemented, pebbly intraformational conglomerate, similar in lithology to those outcrops elsewhere in the Evangeline Member that have produced bone. However, at Longspell Point the rest of the upper Wolfville Formation, which we also place in the Evangeline Member, is present in superposition. The upper Evangeline Member as seen here has a somewhat different lithological character, largely lacking the intraformational conglomerates, with generally smaller fluvial bedforms and numerous deeply rooted palaeosols.
Tectonostratigraphic Sequence III: Blomidon Formation
TS III in the Fundy basin consists entirely of the Blomidon Formation, with the uppermost part of the formation being part of the overlying TS IV. The larger part of the Blomidon Formation constituting TS III consists of a lower, coarser-grained, largely fluvial and aeolian member, the Red Head Member, and a much thicker upper member, the White Water Member (see Appendix for definitions).
Red Head Member
The fluvial and aeolian strata of the Red Head Member are unequivocally exposed in three areas: its type area along the shoreline outcrops of Economy Mountain (Red Head) from Red Head to Lower Economy; at the southern end of Chignecto Provincial Park near Advocate, Nova Scotia; and in the vicinity of Medford, Nova Scotia. Only the last area has yielded tetrapod remains (Figs. 18-19).
Outcrops of the Red Head Member occur in two areas in the vicinity of Medford: on the mainland shore cliffs and foreshore; and at Paddy Island, on the foreshore and along the adjacent mainland shore (Fig. 19). These two areas are separated by a fault with normal displacement of about 30 m (Olsen et al. 1989). Baird and PEO first discovered the productive areas (Fig. 18A-C) in October 1973 (Baird MS, p. 533). Olsen and Baird (1986) and Olsen et al. (1989, 2005a, b) briefly described these outcrops and their fossil assemblages.
Locality A, in the Medford cliff outcrops (Fig. 18D), has yielded a skull and a few associated postcranial fragments (including a nearly complete interclavicle) of the leptopleuronine procolophonid Hypsognathus cf. H. fenneri (NSM998GF45.1; Sues et al. 2000). Aside from its smaller size, the skull is distinguished from other specimens of Hypsognathus fenneri from the Newark Supergroup in having relatively small quadratojugal 'horns, a proportionately shorter snout, and more open cranial sutures, all of which suggest that it is a juvenile. The specimen was discovered by Alton Brown (then of Arco Petroleum) and collected by PEO during a field trip led by Martha Withjack and PEO in 1983.
Localities B and C have yielded a relatively diverse assemblage of trace fossils consisting of both tetrapod burrows and footprints. Cynodontipus was originally considered the track of a hirsute cynodont (Ellenberger 1976), but is now known to represent a tetrapod burrow (unpublished work by PEO, Mohammed Et-Touhami, and Jessica Whiteside). Baird first recorded the presence of this ichnotaxon in 1959, identifying it as a "...problematic double-gouge ichnite..." in his field notes (Baird MS, p. 254). Both terminal burrow bases formed where the animal ended its burrow at a recalcitrant dry mud layer. There are also bedding-parallel traces, where the burrower tunnelled along the interface between dry mud and sand (Fig. 20). The size of burrows varies considerably. The simplest hypothesis is that the burrows were made by Hypsognathus because procolophonids have long been considered burrowing animals (e.g., Groenewald 1991) and this taxon is known from the same horizon. However, especially in view of the variation in size, other burrowing tetrapods may have been involved. Perhaps Cynodontipus-type burrows were made by a variety of tetrapods and represent plesiomorphic digging behaviour at the level of Amniota, using synapomorphybased trace-maker identification (Olsen 1995a; Carrano and Wilson 2001).
Tetrapod tracks from the Red Head Member include Atreipus acadianus (Fig. 21A), Brachychirotherium cf. B. parvum (Fig. 21A), Evazoum sp. (Fig. 21B), and Rhynchosauroides cf. R. brunswickii (Fig. 21C). Most of these tracks occur as natural casts because the underlying mudstones that bear the actual impressions are destroyed during the discovery process. These ichnites are very similar to those from the lower and middle Passaic Formation in the Newark basin of New Jersey and Pennsylvania, and several could be conspecific. However, pending a modern revision of the Passaic Formation material, the identifications proposed here must be considered tentative with the exception of Atreipus acadianus, the holotype of which was collected from the Red Head Member at locality C (Olsen and Baird 1986).
The smallest tetrapod tracks from the Red Head Member (Fig. 21C) are virtually indistinguishable from those of Rhynchosauroides brunswickii (Ryan and Willard 1947, as Kintneria; Baird 1957; Olsen and Flynn 1989). Rhynchosauroides cf. R. brunswickii from the Red Head Member is a quadrupedal trackway with a manus impression smaller than that of the pes, although very similar in digital proportions and with the pes generally being less distinctly impressed. The impressions of manual and pedal digit IV generally project the most, with digits III, II, and I being progressively shorter and digit V short and with a tendency to be recurved. None of the existing specimens shows enough detail to ascertain the phalangeal formula, but, based on other examples of Rhynchosauroides, the phalangeal formulae for both manus and pes are probably 2-3-4-5-3 (e.g., Baird 1957), which is the plesiomorphic count for Amniota. The manus is distinctly smaller than the pes, however, and this appears to be a synapomorphy for Diapsida. Given what we know about Late Triassic continental tetrapods, the most plausible hypothesis is that the trackmaker is a lepidosauromorph such as a rhynchocephalian (Baird 1957) or a small early archosauromorph. Rhynchosauroides cf. R. brunswickii is the most common ichnotaxon in the Red Head Member.
Possible pseudosuchians are represented by quadrupedal trackways very similar to Brachychirotherium parvum (Hitchcock 1889; Baird 1957; Haubold 1971) (Fig. 21A). Baird (1957, p. 473) diagnosed Brachychirotherium parvum as follows: "... phalanges of pes digit V reduced and included in the metatarso-phalangeal pad; pes digit IV and V clawless; narrow, curved claws on pes digits I to III borne high above the thickly padded plantar surface and divergent laterally; metatarso-phalangeal pads III and IV coalesced"
To this, Baird added this description, "the pedal metatarso-phalangeal pads form a straight line of low bosses across the posterior edge of the sole; pedal digit V is encased in a single pad with no claw; and at least digits IV and V of the manus lacked claws" We identify the tracks from the Red Head Member as Brachychirotherium cf. B. parvum because they resemble Brachychirotherium parvum from the Newark basin in overall proportions and share at least the first three nominally diagnostic characters listed by Baird. The tracks from the Red Head Member appear to have separate metatarso-phalangeal pads for pedal digits III and IV but are smaller than any specimen of Brachychirotherium parvum from the Newark basin; it is possible that the difference in pad shape is size-related. The interpretation of the presence of claws on the manus is complicated by the large number of burrow penetrations on the slabs, some of which occur in positions that could be mistaken for impressions left by manual or pedal claws. However, the best-preserved specimens apparently lack claws on manual digits IV and V. The relatively large manus seems to place both the Red Head specimens and Brachychirotherium parvum from the Newark basin in the 'large manus group' of chirotheriid tracks.
Both the absence of claws of pedal digits IV and V and manual digits IV and V are characters seen minimally in Crocodylomorpha. The distribution of these character states outside that clade is poorly documented, because of both the inadequate preservation of known manus and pedes for many taxa and the difficulty of determining whether a small ungual bore a claw. However, claws were definitely present on digits IV and V of the manus and pes of phytosaurs (as evident in the ichnotaxon Apatopus from the Newark basin) and possibly on pedal digit V in the early Middle Triassic archosauriform Euparkeria capensis. The minute ungual phalanges of manual digits III through V and unguals of pedal digits IV and V of the Late Triassic paracrocodylomorph Postosuchus alisonae (Peyer et al. 2008) appear too small and blunt to have borne claw sheaths. The absence of claws on digits IV and V of both manus and pes may represent synapomorphies at some level within the Archosauria, perhaps at the level of Pseudosuchia to the exclusion of Phytosauria.
Unfortunately, the coalescence of manual and pedal phalangeal pads in Brachychirotherium parvum and the Red Head specimens of Brachychirotherium cf. B. parvum precludes determination of the phalangeal formula. However, some members of Pseudosuchia can be ruled out as track makers because of the size of the manus relative to the pes. In at least some paracrocodylomorphs, such as Postosuchus alisonae (Peyer et al. 2008), the manus is relatively smaller than seen in the forms in question. In the Aetosauria, the manus appears relatively larger, although confusion concerning the association of the best manus and pes specimens (see Lucas and Heckert 2011) prevents definitive assessment. Thus the simplest inference is that Brachychirotherium parvum and the Red Head specimens of Brachychirotherium cf. B. parvum represent either crocodylomorphs or another group of pseudosuchians.
A non-dinosaurian dinosauromorph is represented by the tracks of Atreipus acadianus, the type material of which comes from the Red Head Member at locality C (Olsen and Baird 1986; Fig. 21 A). Atreipus acadianus was produced by a habitually quadrupedal tetrapod with a tridactyl pes and a functionally tetradactyl manus. No hallux is evident, even in the deepest impressions, as is also the case in the other North American ichnospecies of Atreipus. Olsen and Baird (1986) argued on phylogenetic grounds that Atreipus was made by either an ornithischian or a member of the sister-group of Dinosauria, which we would now term a non-dinosaurian dinosauromorph. Haubold and Klein (2000), Carrano and Wilson (2001) and Irmis et al. (2007) concurred with this assessment. Subsequently, with the discovery of the dinosauriform Silesaurus from the Late Triassic of Poland (Dzik 2003), it became apparent that at least North American examples of Atreipus also share a potential synapomorphy with Silesaurus to the exclusion of Dinosauria and non-dinosauriform dinosauromorphs. This feature is the distinct reduction in the length of digit I well beyond that seen in basal saurischian dinosaurs but present in the pes of Silesaurus as well as in deeply impressed prints of Atreipus that always lack traces of a hallux. In contrast, deep impressions of Triassic-Early Jurassic brontozoid tracks (sensu Rainforth 2005; traditionally classified as Anchisauripus, Eubrontes and Grallator) always show a trace of the hallux. This suggests that the trackmaker of Atreipus was a member of Dinosauriformes including Silesaurus but excluding Marasuchus, and may well have been a silesaurid, a group now known to have attained a wide geographic distribution during the Triassic (Nesbitt 2011).
Smaller examples of Atreipus acadianus sometimes lack manus impressions, as well as the metatarso-phalangeal impression of pedal digits II and IV that is usually present in North American specimens of Atreipus. Such tracks are easily confused with brontozoid footprints. However, intergradations between all these forms occur even within individual trackways, and thus we think that brontozoid tracks have not yet been found in the Red Head Member and that there is no evidence of coelophysoid theropods in this unit.
The only possible dinosaurian ichnites from the Red Head Member are functionally tridactyl or even didactyl tracks with an unusually elongate digit IV and an apparent trenchant claw on digit II assigned to the ichnogenus Evazoum (Lockley and Lucas 2013; Fig. 21B). This form has previously been referred to as Coelurosaurichnus sp. B (Olsen et al. 1989), "?saurischian dinosaurian track 'new genus 1'" (Olsen and Rainforth 2003) and a 'new dinosaur-like ichnogenus' (Olsen et al. 2005a, b). Lockley et al. (2006) noted the similarity between this form and the ichnogenera Evazoum and Kalosauropus. However, in terms of synapomorphy-based reasoning, this similarity is largely based on retention of plesiomorphic features below the level of Dinosauria, in combination with pedal digitigrady and with bipedality. Lockley and Harris (2011) suggested Evazoum was made by a sauropodomorph, but again the resemblances are all symplesiomorphies below the level of the Dinosauria. Without any distinct pedal synapomorphies relating it to a specific group, we can only conclude that Evazoum might represent an early dinosaur, perhaps even a basal saurischian or a gracile sauropodomorph, but nondinosaurian affinities cannot be ruled out.
The overall assemblage of tetrapod tracks from the Red Head Member is very similar at the level of ichnogenus to that from the middle Passaic Formation of the Newark basin. Most ichnospecies from the Red Head Member are also shared with the middle Passaic except for Atreipus acadianus, which is thus far known only from the Red Head Member. Assemblages from the Passaic Formation also include the presence of Evazoum--CU 170.3 and CU 170.4 were figured and misidentified as coming from the Wolfville Formation by Lockley and Lucas (2013) but are actually from Lyndhurst, New Jersey (Olsen and Rainforth 2003). Based on palaeomagnetic polarity stratigraphy, the Red Head Member is coeval with the middle Passaic Formation (Kent and Olsen 2000), and thus a close correspondence in ichnotaxa is not unexpected.
Outcrops along the shores of Economy Point may pertain to the Red Head Member. Eric Leighton found a single archosauriform tooth crown with serrated edges (NSM014GF023.003) at Thomas Cove (at approximately 45.360042[degrees]N, 63.917850[degrees]W). The strata along this section lie above the unconformity visible on the Consolidated Beacon Resources Ltd. Line 10 seismic profile described in Withjack et al. (2010) and therefore should belong to the Red Head Member. The abundant mud-cracked bedding-plane surfaces in these strata are consistent with this interpretation, although the tooth-producing unit is a calcite-cemented intraformational conglomerate resembling units in the Wolfville Formation.
White Water Member
Overlying the Red Head Member is the White Water Member (defined in Appendix), which crops out at multiple localities along the shores of the Minas Basin and St. Mary's Bay. Through most of its extent, the White Water Member consists of rhythmically bedded sedimentary packages called sand-patch cycles (Smoot and Olsen 1988; Olsen et al. 1989), which formed largely in playas with efflorescent halite crusts. These rhythmic sediments are devoid of tetrapod remains except for one poorly preserved, possible dinosauromorph track (cf. Atreipus; Fig. 22). However, in the shore outcrops on the north side of St. Mary's Bay, especially at Rossway (Figs. 23-24), the sedimentary cycles have much less development of sand-patch fabric and the section is far more fossiliferous, especially with respect to tetrapods; however, all but one locality there have yielded only trace fossils.
Cynodontipus burrows found in the Rossway section may have been produced by procolophonid parareptiles. One particularly informative specimen, found by Jessica Whiteside but unfortunately not collected because of its large size, intertidal location and time constraints, resembles the complex burrow systems reported by Voigt et al. (2011) from the Aglegal Member of the Timezgadiouine Formation of the Argana Basin in Morocco. The Rossway specimen, though, also had clear Cynodontipus-type crescent-shaped scratch marks in positive hyporelief directly attached to the burrows, demonstrating their connection.
One example of Rhynchosauroides sp. was found but not collected by PEO and figured by Olsen et al. (2005a, b; Fig. 24F). It is larger than specimens of Rhynchosauroides brunswickii from the Red Head Member, but additional material is needed for more precise ichnotaxonomic identification. As is the case with the tracks from the Red Head Member, Rhynchosauroides sp. from the White Water Member may represent the tracks of a lepidosauromorph.
The prenarial portion of the cranium of a slendersnouted phytosaur (YPM VPPU 007920), with an associated osteoderm and bone fragments, was found by PEO, Bob Salvia and A. Heimlich in 1974 and represents the only skeletal tetrapod remains yet found from the White Water Member (Fig. 25). This is the only known specimen of a phytosaur from the Fundy basin and the first record of this group from Canada. It is a phytosaurid and was initially identified as Rutiodon sp. (Olsen et al. 1989). However, no synapomorphies have been identified to date that would link the specimen from the Blomidon Formation with the geologically considerably older Rutiodon carolinensis.
One example of cf. Brachychirotherium sp. (Fig. 24E) suggests the presence of Pseudosuchia in the White Water Member, but this specimen is rather indistinctly preserved and not identifiable at a lower ichnotaxonomic level.
Possible silesaurid ornithodirans are represented by several pes impressions. These closely resemble Atreipus milfordensis in their distinctive 'tulip' shape (Fig. 24D). However, they all lack definitive manus impressions, and thus identification is somewhat uncertain.
The Rossway locality is noteworthy for having yielded the only definitive brontozoid footprints from strata below the basalt in the Fundy basin, and thus they represent the only pre-basalt evidence for theropod dinosaurs in this region. Two large slabs were found (PEO, Amy Litt, and Louise Roth in August 1976; PEO and Dan Simanek in July 1978), but neither could be collected (Fig. 24A-B). The brontozoid tracks have a proportionately long pedal digit III, with (when well-preserved) well-developed pads, especially the most distal, a relatively narrow pes with low angulation, and a tendency for the metatarso-phalangeal pad of digit IV not to leave an impression. Following the classification of Lull (1953), these tracks would be identified as Anchisauripus sillimani or Anchisauripus tuberosus but, as Olsen et al. (1998) argued, the proportional features traditionally employed to differentiate the ichnogenera Anchisauripus, Grallator and Eubrontes are size-related along a morphological continuum. Identification as theropod tracks is based on their functionally tridactyl nature, with a distinct hallux (not actually seen in these specimens), and full bipedality. However, it is possible that some as yet unknown non-dinosaurian dinosauriforms had a similar foot structure that, based on tracks, might not be separable from that of theropods. However, the fact that identical footprints occur in Early Jurassic strata from which no nondinosaurian dinosauriforms are known and in which the only plausible makers of brontozoid tracks are theropod dinosaurs lends support to the original identification.
In overall composition, the footprint assemblage from the Rossway locality most closely resembles that from the lower part of the upper Passaic Formation (roughly between the Metlars Member and Member OO; Olsen et al. 1996) in the presence of medium-sized brontozoid tracks but with Atreipus still present. This would correlate with the lower to middle White Water Member on the Medford shore, east at Blomidon, above the level of the Red Head Member track assemblage. There is as yet no independent test for this hypothesized correlation.
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|Title Annotation:||p. 139-167|
|Author:||Sues, Hans-Dieter; Olsen, Paul E.|
|Date:||Jan 1, 2015|
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