Early tetrapod likely ate on shore.The skull structure of Acanthostega, a semiaquatic sem·i·a·quat·ic adj. Adapted for living or growing in or near water; not entirely aquatic: a semiaquatic plant or animal. creature that lived about 365 million years ago, suggests that although the creature spent most of its time in the water, it fed on shore or in the shallows rather than in deep water. Molly J. Markey, a paleontologist at Harvard University, examined the pattern of boundaries between skull bones in Acanthostega. The boundaries, called sutures, can have straight edges or jagged, interlocking interlocking /in·ter·lock·ing/ (-lok´ing) closely joined, as by hooks or dovetails; locking into one another. interlocking Obstetrics A rare complication of vaginal delivery of twins; the 1st edges. The pattern of skull sutures in Acanthostega doesn't match the one found in Polypterus, a modern fish that, like most fish today, captures its prey by slurping See pod slurping. it in (SN: 4/24/04, p. 264), or the pattern found in Eusthenopteron, a fish that lived about 385 million years ago and seems to have been a suction feeder. Both creatures had a straight-edged suture suture /su·ture/ (soo´cher) 1. sutura. 2. a stitch or series of stitches made to secure apposition of the edges of a surgical or traumatic wound. 3. to apply such stitches. 4. running along the top center of its skull. In contrast, the suture layout in Acanthostega's skull closely resembles the pattern found in the skull of Phonerpeton, an amphibian amphibian, in zoology amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the that lived and presumably pre·sum·a·ble adj. That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. fed on land around 300 million years ago. Markey has measured the strains across straight and jagged sutures in Polypterus skulls as the fish ate. From her results, she speculates that the Polypterus and Eusthenopteron pattern successfully resists the stresses that arise during slurping, while the Phonerpeton and Acanthostega pattern would better resist the stresses during grab-and-bite dining. Therefore, Markey suggests that Acanthostega fed on shore or in shallow water.--S.P. |
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