Fred Ruhe
Well-known member
Poster Session III (Friday, October 19, 2018, 4:15–6:15 PM)
Peter A. KLOESS, Ashley W. POUST & Thomas STIDHAM, 2018
A PARTIAL DENTARY FROM A LARGE BONY-TOOTHED BIRD (AVES:
PELAGORNITHIDAE) FROM THE EOCENE LA MESETA FORMATION OF
SEYMOUR ISLAND, ANTARCTICA
Abstracts book for the Society of Vertebrate Paleontology 2018 meeting October 17-20, 2018
Free pdf: http://vertpaleo.org/Annual-Meeting...P-2018-program-book-V4-FINAL-with-covers.aspx
Abstract
Bony-toothed birds (Odontopterygiformes: Pelagornithidae) are a cosmopolitan, pelagic clade of large, volant birds known from the late Paleocene to the late Pliocene. The readily diagnostic characteristic of this clade is the modification of the tomial crest of the premaxillae, maxillae, and mandibles into a variety of tooth-like bony projections lacking any dental mineralization (or homology to teeth). The size and spacing of these projections vary across the clade and are consistent within species, following a set sequence of large and smaller pseudoteeth covered by the rhamphotheca. We report a new partial dentary of a bony-toothed bird from Antarctica, discovered from the highest stratigraphic unit within the middle to late Eocene La Meseta Formation (Telm 7) of Seymour Island, peninsular Antarctica. This >12 cm long partial left dentary derives from a region of the mandible rostral to the intraramal joint, and preserves the remains of four low, worn pseudoteeth. Based on the regular pattern of pseudotooth spacing, a couple of bony projections may have been worn away, and the past occurrence of smaller intermediately spaced pseudoteeth cannot be ruled out. However, there are no exposed neurovascular openings that would be associated with the broken or worn base of such smaller pseudoteeth. As in other known pelagornithids, the mandibular fragment also preserves the medial and lateral rostrocaudally oriented groove and lamina on the ventral aspect of the fragment. Given the size of the specimen, the morphology and pattern of the preserved pseudoteeth, and the age of the fossiliferous sediments (late Eocene), an affinity possibly with a Dasornis or Lutetodontopteryx-like pelagornithid is likely (and consistent with the allocation of the published La Meseta tarsometatarsus as similar to the Dasornis morphotype). The Eocene La Meseta pelagornithid specimens (from a large-sized species) suggest the presence of an extinct (possibly unnamed) species larger than some known Eocene taxa. The addition of this fossil record reinforces the ideas that along with penguins, pelagornithids were among the common and dominant avian clades of Antarctica in the Eocene, and that they would have occupied a high trophic role in the Antarctic seas, today filled by albatrosses and other pelagic avian clades.
Enjoy,
Fred
Peter A. KLOESS, Ashley W. POUST & Thomas STIDHAM, 2018
A PARTIAL DENTARY FROM A LARGE BONY-TOOTHED BIRD (AVES:
PELAGORNITHIDAE) FROM THE EOCENE LA MESETA FORMATION OF
SEYMOUR ISLAND, ANTARCTICA
Abstracts book for the Society of Vertebrate Paleontology 2018 meeting October 17-20, 2018
Free pdf: http://vertpaleo.org/Annual-Meeting...P-2018-program-book-V4-FINAL-with-covers.aspx
Abstract
Bony-toothed birds (Odontopterygiformes: Pelagornithidae) are a cosmopolitan, pelagic clade of large, volant birds known from the late Paleocene to the late Pliocene. The readily diagnostic characteristic of this clade is the modification of the tomial crest of the premaxillae, maxillae, and mandibles into a variety of tooth-like bony projections lacking any dental mineralization (or homology to teeth). The size and spacing of these projections vary across the clade and are consistent within species, following a set sequence of large and smaller pseudoteeth covered by the rhamphotheca. We report a new partial dentary of a bony-toothed bird from Antarctica, discovered from the highest stratigraphic unit within the middle to late Eocene La Meseta Formation (Telm 7) of Seymour Island, peninsular Antarctica. This >12 cm long partial left dentary derives from a region of the mandible rostral to the intraramal joint, and preserves the remains of four low, worn pseudoteeth. Based on the regular pattern of pseudotooth spacing, a couple of bony projections may have been worn away, and the past occurrence of smaller intermediately spaced pseudoteeth cannot be ruled out. However, there are no exposed neurovascular openings that would be associated with the broken or worn base of such smaller pseudoteeth. As in other known pelagornithids, the mandibular fragment also preserves the medial and lateral rostrocaudally oriented groove and lamina on the ventral aspect of the fragment. Given the size of the specimen, the morphology and pattern of the preserved pseudoteeth, and the age of the fossiliferous sediments (late Eocene), an affinity possibly with a Dasornis or Lutetodontopteryx-like pelagornithid is likely (and consistent with the allocation of the published La Meseta tarsometatarsus as similar to the Dasornis morphotype). The Eocene La Meseta pelagornithid specimens (from a large-sized species) suggest the presence of an extinct (possibly unnamed) species larger than some known Eocene taxa. The addition of this fossil record reinforces the ideas that along with penguins, pelagornithids were among the common and dominant avian clades of Antarctica in the Eocene, and that they would have occupied a high trophic role in the Antarctic seas, today filled by albatrosses and other pelagic avian clades.
Enjoy,
Fred
