tulerpeton skeleton

Tulerpeton curtum

Tulerpeton curtum was recovered from the Tula Region of Russia. It's remains are more complete than those of most Late Devonian tetrapods. (Although they are substantially less complete than those of Acanthostega and Ichthyostega.) These include a nearly complete pectoral girdle, forelimb and hindlimb, fragments from the skull (premaxilla and vomer) and numerous small belly scutes.

Perhaps Tulerpeton's most famous characteristic is the number of digits (6) on its front and hind limbs. Similar findings in Acanthostega and Ichthyostega suggest that the five-fingered pattern found in later tetrapod lineages did not evolve until the Carboniferous. The digits are relatively enongated and slender, which suggest a more terrestrial habit. However, the ankle joints and the muscle attachment structures of the femur indicate that the hind limbs were better suited to paddling that crawling.

Tuleperton's pectoral girdle (shoulder bones) is more robust than that of Acanthostega, suggesting that it was somewhat less aquatic. In addition, the pectoral girdle lacked a post-branchial lamina, indicating that Tulerpeton did not have internal gills. On the other hand, it retains an anocleithrum (a part of the upper pectoral), which was lost in Ichthyostega and Hynerpeton, but is present in Acanthostega. The anatomy of the humerus (upper arm) suggest a closer relationship with Carboniferous anthrocasaurian amphibians than with either Acanthostega or Ichthyostega.

Tulerpeton was recovered from what appears to be marine-influenced eustarine deposits. In contrast, most of the other Famennian tetrapods were recovered from freshwater deposits. It may be that at least some of the early tetrapods retained physiological adaptations that would enable them to cross marine barriers, and may help explain the nearly worldwide tropical distribution from Euramerica (North America and northern Europe) to eastern Gondwana (Australia) of early tetrapods.

A number of isolated tetrapod elements (i.e., interclavicles, ribs, vertebrae, part of the pelvis and skull fragments) have been recovered near where the articulated remains of Tulerpeton were found. These exhibit two different patterns of surface ornamentation which suggest that Tulerpeton is not the only tetrapod present.

A variety of other vertebrates were associated with Tulerpeton. These include unidentified acanthodians, two antiarch placoderms (Bothriolepis and Remigolepis), an onychodont lobe-fin (Strunius), a lungfish (Andreyevichthys), a trischopterid lobe-fin (Eusthenodon), acanthodians, ray-fins and chondrichthyans.

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Web:
G.R. Morton's Transitional Forms: Fish to Amphibian:
home.entouch.net/dmd/transit.htm
Books:
Clack, J.A. 2002. Gaining Ground: The Origin and Early Evolution of Tetrapods. Bloomington: Indiana Univ. Press.
Janvier, P. 1996. Early Vertebrates. Oxford: Claredon Press.
Scientific Papers
Clack, J.A. 1997. "Devonian tetrapod trackways and trackmakers: a review of the fossils and footprints". Paleogeography, Paleoclimatology, Paleoecology 130: 227-250.
Lebedev, O.A. 1984. "The first find of a Devonian tetrapod in USSR." Doklady Akad. Navk. SSSR. 278: 1407-1413. (in Russian)
Lebedev, O.A. and J.A. Clack. 1993. "Upper Devonian tetrapods from Andreyeva, Tula Region, Russia." Paleontology 36(3): 721-734.
Lebedev, O.A. and M.I. Coates. 1995. "The postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev". Zoological Journal of the Linnean Society 114: 307-348.
Daeschler, E.B. and N. Shubin. 1995. "Tetrapod Origins." Paleobiology 21(4): 404-409.

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