Physornis fortis Ameghino, 1895

Alvarenga, Herculano M. F. & Höfling, Elizabeth, 2003, Systematic Revision Of The Phorusrhacidae (Aves: Ralliformes), Papéis Avulsos de Zoologia 43 (4), pp. 55-91 : 68-69

Physornis fortis Ameghino, 1895

Physornis fortis Ameghino, 1895:576 ; Brodkorb, 1967. Aucornis euryrhyncus Ameghino, 1898:9 ; Brodkorb, 1967

(syn. of Physornis fortis ).

Type – A fragment around 137 cm in length, constituting the ventral portion of the mandibular symphysis and the adjacent part of the right mandibular branch ( BMNH-A583 : Fig. 14 ) .

A proximal portion of the left tarsometatarsus (MACN-A-52-185, Figs. 2A and 13 ). A rostral extremity of the mandibular symphysis (MACN-A-52-186). A phalanx 1 of the toe II from the left foot (MACN-A-52-187); these last three bones were associated and served as type for Ancornis euryrhyncus Ameghino, 1898 . A phalanx 1 of the toe IV from the left foot (MACN-A-52-188). In the Museum of Amherst College , Massachussetts, U.S.A., there is also a right femur, incomplete on the proximal extremity, without number (?), refered to and figured by Loomis (1914:226) .

Horizon and Locality – Middle to Upper Oligocene of Argentina (Deseadan). Province of Santa Cruz, Argentina: Puerto Deseado, Punta Nova, La Flexa, in the levels of occurrence of Pyrotherium . For a better indication of the geological age, see Mac Fadden (1985) and Marshall et al. (1986).

Measurements – Table 3.

Illustrations – Loomis, 1914: Fig. 149.

Remarks – The size of the mandibular symphysis (type: BMNH-A583), originally described by Ameghino (1895), is in perfect agreement with the two measured specimens in the Field Museum of Chicago ( Table 3). A flat (not convex) region in the mid-ventral portion of the symphysis is noted in all the specimens.

The branches of the mandible of Physornis , in comparison with those of Phorusrhacos , are really more further apart from the median line, as in the original description by Ameghino (op. cit.), which implies a skull with a wider base. Ameghino perfectly described the only large built Phorusrhacidae of the stratigraphic layers characterized by the presence of Pyrotherium (Deseadan) . Thus, there is no reason for the rejection of the genus Physornis and the species P. fortis , as being indeterminate, as suggested by Patterson (1941).

Although the complete shape of the tarsometatarsus of Physornis is unknown, the proximal portion of this is shown to be quite flattened in the dorsoventral extent. Associating this to the short and wide mandibular symphysis, besides the quite large build, it fits in perfectly amongst the Brontornithinae .

Aucornis solidus Ameghino, 1898 , considered by Brodkorb (1967) as synonymous of Physornis fortis , was created only based on a proximal extremity of a phalanx (MACN-A-52-110), of a much smaller-sized bird than Physornis fortis , possibly synonymous of Andrewsornis abbotti Patterson, 1941 , which should be left as a species inquirenda, seeing that one is dealing with an absolutely insufficient segment to diagnose a species.

The two symphysis examined in the Field Museum of Chicago, showed an interesting difference on the dorsal surface, which, almost flat in FM-P13340, forms a longitudinal channel in FM-P13340 ( Figs. 12C and 12D ). These differences were interpreted as being individual variation.

Figures

FIGURE 2. Dorsal view of the tarsometatarsi of the Brontornithinae (A-D) and Phorusrhacinae (E-F):A - Physornis fortis (MACN-A-52-185); B - Paraphysornis brasiliensis (DGM-1418-R); C - Brontornis burmeisteri (FM-P13259); D - Brontornis burmeisteri (lectotype MLP-91); E - Phorusrhacos longissimus (MLP-76.V.10.11, type of Liornis minor Dolgopol de Saez, 1927); F - Devincenzia pozzi (MNHN-M-189, type of Devincenzia gallinali Kraglievich, 1932).A-D left side; E-F right side.

FIGURE 12. Physornis fortis; symphysis with a part of the left mandibular branch (FM-P13340) in views: A - ventral, B - left lateral, C - dorsal, D - mandibular symphysis (FM-P13619) in dorsal view.

FIGURE 13. Proximal end of the left tarsometatarsus of Physornis fortis (MACN-A-52-185) in views: A - proximal, B - medial, C - dorsal, D - lateral and E - plantar. This specimen appears to be associated to the fragment of mandibular symphysis (MACN-A-52-186) and served as type for Aucornis euryrhynchus Ameghino, 1899.

FIGURE 14. Fragment of the symphysis and right mandibular branch of Physornis fortis (type: BMNH-A583) ventral (A) and dorsomedial (B) views. Compare with Fig. 12A.