Pelagornithids from the Eocene of Antarctica (1 Viewer)

Acosta Hospitaleche, C. and M. Reguero (2020)
Additional Pelagornithidae remains from Seymour Island, Antarctica
Journal of South American Earth Sciences (advance online publication)
doi: 10.1016/j.jsames.2020.102504
https://www.sciencedirect.com/science/article/pii/S0895981120300171

Two incomplete mandibles are assigned to Pelagornithidae given the presence of a well marked neurovascular furrow and the unique bony projections, or “pseudo-teeth”, along the crista tomialis. Specimens IAA-Pv 175 from Ypresian levels of La Meseta Alloformation (Cucullaea I Allomember), and IAA-Pv 823 from Bartonian beds of the Submeseta Alloformation, in Seymour Island (Antarctic Peninsula, West Antarctica) corresponds to the morpho-type 1, previously proposed for Antarctic pseudo-tooth birds.

The intermediate condition of the pseudo-teeth of these specimens reinforces the idea that diet changed from piscivory to molluscivory along the evolutive history of the group.

Systematic Paleontology

Aves Linnaeus, 1758
Odontopterygiformes Howard, 1957
Pelagornithidae Fürbringer, 1888
Pelagornithidae Indet. Morpho-Type 1

Material. IAA-PV 175 medio-rostral portion of the left ramus mandibulae

Provenance. Locality IAA 1/90 (Seymour Island), Cucullaea Allomember (La Meseta Alloformation), Ypresian (lower Eocene).

Material. IAA-Pv 823 rostral portion of left ramus mandibulae

Provenance. Locality DPV 13/84 (Seymour Island), Submeseta II Allomember (Submeseta Alloformation), Bartonian (middle Eocene).


Pelagornithidae indet. assigned here to morpho-type 1: A, C, E. Medio-rostral portion of the left ramus mandibulae IAA-PV 175 (A, lateral; C, dorsal; and E, medial views); B, D, F. Rostral portion of left ramus mandibulae IAA-Pv 823 (B, lateral; D, dorsal; and F, medial views). The arrows between both specimens indicate the cranial end of the mandibles. The schematic drawing show the pseudo-teeth pattern explained in the descriptions. The arrows in the fourth order denticles indicate a more medial position, the asterisk points a broken area of the bones, and the question marks show doubtful structures. Scale bar for each specimen is 1 cm.

Fred

A response to this paper:

Chávez Hoffmeister, M. and P. Oyanadel Urbina (2020)
Reply to C. Acosta Hospitaleche and M. Reguero (2020) additional pelagornithidae remains from Seymour Island, Antarctica
Journal of South American Earth Sciences (advance online publication)
doi: 10.1016/j.jsames.2020.102643
https://www.sciencedirect.com/science/article/pii/S0895981120301565

Acosta Hospitaleche and Reguero (2020) report the discovery of two mandibular fragments collected during 2016 and 2017 in Seymour Island, Antarctica, and assign them as Pelagornithidae indet. Morpho-Type 1. However, based on the published pictures of both specimens, it is clear that only IAA-PV 175 can be tentatively assigned to Pelagornithidae, whereas IAA-PV 823 truly belongs to a bony fish. Although this reasignation does not invalidate the general content and conclusions of their publication, we consider this reply important in order to clarify the assignation of IAAPV 823 and bring attention to the implications of this new interpretation in regards to the fossil record of fishes in the Southern Hemisphere.

Some explanation on the figure in post # 2:

Fig. 1. Pelagornithidae indet. assigned here to morpho-type 1: A, C, E. Medio-rostral portion of the left ramus mandibulae IAA-PV 175 (A, lateral; C, dorsal; and E, medial views); B, D, F. Rostral portion of left ramus mandibulae IAA-Pv 823 (B, lateral; D, dorsal; and F, medial views). The arrows between both specimens indicate the cranial end of the mandibles.
Scale bar for each specimen is 1 cm.

Fred