Aizenogyps
| Aizenogyps | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Accipitriformes |
| Family: | Cathartidae |
| Genus: | †Aizenogyps Emslie, 1998 |
| Species: | †A. toomeyae |
| Binomial name | |
| †Aizenogyps toomeyae Emslie, 1998 | |
Aizenogyps is an extinct genus of new world vulture from the latest Pliocene of Florida.
History and naming
[edit]The fossils of Aizenogyps have been recovered from Lates Pliocene (Blancan) deposits at Haile 7C, a fossil locality in Alachua County, Florida. The genus was established by Steven D. Emslie in 1998 based on a complete left tarsometatarsus, though a number of other remains not found in association with the type specimen, namely fifteen neck vertebrae, the third vertebra of the torso and a left upper arm bone were referred to the taxon as paratypes.[1]
The name Aizenogygps derives from the Greek words "aizeno", which translates to "powerful" or "vigorous", and "gyps", meaning vulture. The species name honors Barbara Toomey, who was responsible for the discovery of some of the material used in naming the genus and contributed to Floridian paleontology beyond that.[1]
Description
[edit]The shaft of the tarsometatarsus of Aizenogyps is described by Emslie as having been broader and more robust those of all fossil and living cathartids known at the time including the modern Californian and Andean condors. The shaft is collumnar (straight) as in Hadrogyps and lacks the distinct flaring present towards both ends seen in the extant genera as well as Brasilogyps and Pliogyps. The anterior metatarsal groove is deeper towards the bone's articulation with the tibiotarsus and stretches across over half the length of the shaft like in modern king vultures. The distal and proximal foramina are small rather than large as in Hadrogyps or even moderately-large like in Pliogyps. The intercotylar prominence, located at the bone's proximal end, features a deep notch in its surface that is either only shallow or entirely absent across modern cathartids. Similarily the intercotylar depression, which is shallow and small across extant genera, is described as large, round and deeply excavated. Observing the tarsometatarsus from behind shows that the hypotarsus is nearly as deep as it is wide, forming a broad plate similar to what is seen in the genus Coragyps, today's black vulture. It also somewhat resembles the genus Cathartes, which includes the turkey vulture, in lacking a notch in the proximal edge of the hypotarsus. Internal to the ridge that extends downward from the hypotarsus the tarsometatarsal shaft is deeply excavated, unlike in modern cathartids where this excavation is only described as shallow to moderately deep. The ridges bordering the internal and external borders of the posterior tarsometatarsus are also well developed, with Emslie describing them as high and distinct as opposed to the shallow ridges observed in extant forms. At the other end of the tarsometatarsus the metatarsal facets are positioned in a way that places them closer to the internal side of the shaft like in turkey vultures and Andean condors, whereas in Californian condors, king and turkey vultures they extend much further proximally. In addition to that, the shaft is noteably depressed above the trochleae, whereas in extant genera and Geronogyps such a depression is absent or at most shallow. Finally, the middle trochlea, which corresponds to the third (middle) toe is relatively short like in Californian condors.[1]
The deltoid crest of the humerus is broad and flared and extends relatively far distally before merging into the shaft of the bone, a trait shared with smaller cathartids like Cathartes and Coragyps as well as the larger Geronogyps. This contrasts with the two extant condor species and the king vulture, in which the crest is shallower and disappears into the shaft further up. The internal border of the crest is large and raised clearly above the shaft, whereas in modern forms and Geronogyps it either remains flush with the shaft is is at most slightly raised. The crest ultimately ends in an oblong tubercle that is larger than in modern new world vultures. The pneumatic foramen of the upper arm are shallow with broad, rounded borders, a feature shared by Cathartes, while other modern cathartids have deeper foramina or in the case of Gymnogyps narrower borders. The groove that separates the humeral head from the internal tuberosity is deep where it is shallow in Gymnogyps, only moderately deep in Vultur and Sarcorhamphus and at least partially to fully pneumatized in both Cathartes and Coragyps. The impression left by the brachialis anticus muscle are not pneumatized, which sets Aizenogyps apart from black vultures, and compared to turkey vultures the impression left is not as elongated. The point of attachment for the anterior articular ligament is described as broader than what is seen in the Californian condor and turkey vultures, instead being more comparable to the anatomy seen in the Andean condor.[1]
Emslie describes Aizenogyps as having reached a size comparable to that of Dryornis, though the latter is slightly larger.[1]
Paleobiology
[edit]Aizenogyps is one of several condors known from the Pliocene to Pleistocene of Florida alongside the Californian condor and its close relative Gymnogyps kofordi. In addition to the type material from Haile 7C, remains previously assigned to Gymnogyps from the contemporary Macasphalt Shell Pit and Inglis IA may also be referable to Aizenogyps.[1]