28 research outputs found
Late Devonian paleontology and paleoenvironments at Red Hill and other fossil sites in the Catskill Formation of north-central Pennsylvania
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The feeding system of <i>Tiktaalik roseae</i>: an intermediate between suction feeding and biting
Changes to feeding structures are a fundamental component of the vertebrate transition from water to land. Classically, this event has been characterized as a shift from an aquatic, suction-based mode of prey capture involving cranial kinesis to a biting-based feeding system utilizing a rigid skull capable of capturing prey on land. Here we show that a key intermediate, Tiktaalik roseae, was capable of cranial kinesis despite significant restructuring of the skull to facilitate biting and snapping. Lateral sliding joints between the cheek and dermal skull roof, as well as independent mobility between the hyomandibula and palatoquadrate, enable the suspensorium of T. roseae to expand laterally in a manner similar to modern alligator gars and polypterids. This movement can expand the spiracular and opercular cavities during feeding and respiration, which would direct fluid through the feeding apparatus. Detailed analysis of the sutural morphology of T. roseae suggests that the ability to laterally expand the cheek and palate was maintained during the fish-to-tetrapod transition, implying that limited cranial kinesis was plesiomorphic to the earliest limbed vertebrates. Furthermore, recent kinematic studies of feeding in gars demonstrate that prey capture with lateral snapping can synergistically combine both biting and suction, rather than trading off one for the other. A “gar-like” stage in early tetrapod evolution might have been an important intermediate step in the evolution of terrestrial feeding systems by maintaining suction-generation capabilities while simultaneously elaborating a mechanism for biting-based prey capture
Terrestrialization in the Late Devonian: A palaeoecological overview of the Red Hill site, Pennsylvania, USA
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Fin ray patterns at the fin-to-limb transition
The fin-to-limb transition was marked by the origin of digits and the loss of dermal fin rays. Paleontological research into this transformation has focused on the evolution of the endoskeleton, with little attention paid to fin ray structure and function. To address this knowledge gap, we study the dermal rays of the pectoral fins of 3 key tetrapodomorph taxa—Sauripterus taylori (Rhizodontida), Eusthenopteron foordi (Tristichopteridae), and Tiktaalik roseae (Elpistostegalia)—using computed tomography. These data show several trends in the lineage leading to digited forms, including the consolidation of fin rays (e.g., reduced segmentation and branching), reduction of the fin web, and unexpectedly, the evolution of asymmetry between dorsal and ventral hemitrichia. In Eusthenopteron, dorsal rays cover the preaxial endoskeleton slightly more than ventral rays. In Tiktaalik, dorsal rays fully cover the third and fourth mesomeres, while ventral rays are restricted distal to these elements, suggesting the presence of ventralized musculature at the fin tip analogous to a fleshy “palm.” Asymmetry is also observed in cross-sectional areas of dorsal and ventral rays. Eusthenopteron dorsal rays are slightly larger than ventral rays; by contrast, Tiktaalik dorsal rays can be several times larger than ventral rays, and degree of asymmetry appears to be greater at larger sizes. Analysis of extant osteichthyans suggests that cross-sectional asymmetry in the dermal rays of paired fins is plesiomorphic to crown group osteichthyans. The evolution of dermal rays in crownward stem tetrapods reflects adaptation for a fin-supported elevated posture and resistance to substrate-based loading prior to the origin of digits
Presentation of the 2007 Harrel L. Strimple Award of the Paleontological Society to Norman D. Rowe
Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania
A late Irvingtonian assemblage of fossils at Port Kennedy, Montgomery County, Pennsylvania (today within the Valley Forge National Historical Park) was discovered in a filled solution feature first exposed in a quarry wall in 1870. The remnants of the deposit are buried today. Yielding specimens mostly of vertebrates, but including plants and beetle fragments, the deposit was well-studied by scientists of the late 1800s, most notably Edward Cope. In the last century, only systematically focused papers and reviews of Pleistocene faunas have discussed the Port Kennedy fossils. Mention of the plant material is made only in passing, and nothing more has been said of the (now missing) insect specimens. Furthermore, nothing has been discussed of the geology and taphonomy of the deposit and its fossils with the perspective of current geologic principles. This paper summarizes in this more modern view the known information about the deposit and its fossils. Revised and new information on taxonomy and status of specimens is provided, including new records and notice of the recovery of the holotype of the skunk Brachyprotoma obtusata (Cope, 1899) (Mammalia: Carnivora)
Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania
A late Irvingtonian assemblage of fossils at Port Kennedy, Montgomery County, Pennsylvania (today within the Valley Forge National Historical Park) was discovered in a filled solution feature first exposed in a quarry wall in 1870. The remnants of the deposit are buried today. Yielding specimens mostly of vertebrates, but including plants and beetle fragments, the deposit was well-studied by scientists of the late 1800s, most notably Edward Cope. In the last century, only systematically focused papers and reviews of Pleistocene faunas have discussed the Port Kennedy fossils. Mention of the plant material is made only in passing, and nothing more has been said of the (now missing) insect specimens. Furthermore, nothing has been discussed of the geology and taphonomy of the deposit and its fossils with the perspective of current geologic principles. This paper summarizes in this more modern view the known information about the deposit and its fossils. Revised and new information on taxonomy and status of specimens is provided, including new records and notice of the recovery of the holotype of the skunk Brachyprotoma obtusata (Cope, 1899) (Mammalia: Carnivora)
Review and New Data on the Port Kennedy Local Fauna and Flora (Late Irvingtonian), Valley Forge National Historical Park, Montgomery County, Pennsylvania
A late Irvingtonian assemblage of fossils at Port Kennedy, Montgomery County, Pennsylvania (today within the Valley Forge National Historical Park) was discovered in a filled solution feature first exposed in a quarry wall in 1870. The remnants of the deposit are buried today. Yielding specimens mostly of vertebrates, but including plants and beetle fragments, the deposit was well-studied by scientists of the late 1800s, most notably Edward Cope. In the last century, only systematically focused papers and reviews of Pleistocene faunas have discussed the Port Kennedy fossils. Mention of the plant material is made only in passing, and nothing more has been said of the (now missing) insect specimens. Furthermore, nothing has been discussed of the geology and taphonomy of the deposit and its fossils with the perspective of current geologic principles. This paper summarizes in this more modern view the known information about the deposit and its fossils. Revised and new information on taxonomy and status of specimens is provided, including new records and notice of the recovery of the holotype of the skunk Brachyprotoma obtusata (Cope, 1899) (Mammalia: Carnivora)