Physornis 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 : 66-68

Genus Physornis Ameghino, 1895

Physornis Ameghino, 1895:576 ; Brodkorb, 1967. Aucornis Ameghino, 1898:9 ; Brodkorb, 1967 (syn. of

Physornis ).

Type Species – Physornis fortis Ameghino, 1895 .

Included Species – Only the type species.

Distribution – Middle and Upper Oligocene of Argentina.

Diagnosis Revised – Of a gigantic size, rivaling with Brontornis . A very short and wide mandibular symphy- sis, characteristically with an almost flat ventral surface in the mid-portion ( Fig. 12 and e. g. Alvarenga, 1993: Fig. 1 ). The lateral cotyl of the tarsometatarsus is almost quadrangular, when viewed proximally ( Fig. 13A ). The lateral edge of the hipotarsus, when viewed from the rear, forms a prominent crest which distiguishes it well from Brontornis and Paraphysornis ( Fig. 13 and e. g. Alvarenga, 1993: Fig. 2 ).

Remarks – The genus Physornis and its type species P. fortis , were described by Ameghino in 1895, based on a fragment of the mandible comprehending part of the symphysis and the right branch, this description, unfortunately, not being accompanied by an illustration.

Patterson (1941:52) examined the type of Physornis fortis , nowadays deposited in the museum of London (BMNH-A583), arriving at the conclusion that this is a bony fragment without any morphological characteristic, possibly being the iliac crest of a mammal, thus proposing the rejection of the terms, both for the genus as well as the species, as being indeterminate. We had also the opportunity of examining the aforementioned type material ( Fig. 14 ), arriving at the Hypodigm – Type; a mandibular symphysis, including a part of the left branch ( Figs. 12 A-C), associated to the caudal portion of the left quadratojugal ( Fig. 15A ), and to the atlas ( Fig. 16A ), besides fragments of vertebras, phalanges etc. (FM-P13340). A well conserved madibular symphysis ( Fig. 12D ), associated to the caudal extremity of the right quadratojugal (FM-P13619). conclusion that this is undoubtedly a fragment of the symphysis and part of the right branch of a large Phorusrhacidae . The experience acquired in the restoration of the mandible of Paraphysornis (Alvarenga, 1982) , contributed to us for the immediate recognition of the texture of a real mandibular symphysis of a Phorusrhacidae . Further, it is evident that Ameghino had prior experience, having examined and described several other mandibular symphysis of Phorusrhacidae , such as, Phorusrhacos longissimus Ameghino, 1887 ; Phororhacos sehuensis Ameghino, 1891; Phororhacos platygnathus Ameghino, 1891; Tolmodus inflatus Ameghino, 1891 , and others, this showing his intimacy with this anatomical portion, which, apparantly, is often conserved in the Phorusrhacidae fossils.

Although it is an almost shapeless fragment and, thus, very inadequate for typifying a species, the type demonstrates, besides the size and the geographical and stratigraphical source, also the flat portion of the ventral surface of the mandibular symphysis, which is characteristic of this genus ( Figs. 12A and 14 ).

Figures

FIGURE 1. Reproduction (by E. Brettas) of some Phorusrhacidae keeping the due proportion as to size. The silhouette of a man 1.75 m high is used as a scale. A - Brontornis burmeisteri; B - Paraphysornis brasiliensis; C - Phorusrhacos longissimus; D - Andalgalornis steuletti; E - Psilopterus bachmanni; F - Psilopterus lemoinei; G - Procariama simplex; H - Mesembriornis milneedwardsi.

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.

FIGURE 15. Caudal portion of the left quadratojugal, in medial view of: A - Physornis fortis (FM-P13340); B - Paraphysornis brasiliensis (DGM-1418-R).

FIGURE 16. Atlas of A - Physornis fortis (FM-P13340); B - Paraphysornis brasiliensis (DGM-1418-R).Cranial (above) and right lateral (below) views. Physornis possesses more volume and articular surface for the occipital condyle.