Brontornis burmeisteri Moreno & Mercerat, 1891

Alvarenga, Herculano M. F. & Höfling, Elizabeth, 2003, Systematic Revision Of The Phorusrhacidae (Aves: Ralliformes), Papéis Avulsos de Zoologia 43 (4), pp. 55-91 : 65-66

Brontornis burmeisteri Moreno & Mercerat, 1891

Brontornis burmeisteri Moreno & Mercerat, 1891:37 ; Brodkorb, 1967.

Rostrornis floweri Moreno & Mercerat, 1891:40 ; Brodkorb 1967 (syn. of B. burmeisteri ).

Brontornis platyonyx Ameghino, 1895 ; Brodkorb 1967 (syn. of B. burmeisteri ).

Lectotypes – The left femur, tibiotarsus, fibula and tarsometatarsus (MLP-88-91), certainly belonging to the same individual, designated by Brodkorb (1967).

Hypodigm – lectotypes; portion of the mandible including the symphysis and part of the right branch (MHNP-1902-6, Fig. 7 ); two large fragments of the

Brontornis Moreno & Mercerat, 1891 :20,37; Brodkorb, 1967.

Rostrornis Moreno & Mercerat, 1891 :20,40; Brodkorb, 1967 (syn. of Brontornis ).

Type Species – Brontornis burmeisteri Moreno & Mercerat, 1891 .

Included Species – Only the type species.

Distribution – Lower to Mid-Miocene in Argentina.

Diagnos i s Revised – Certainly the biggest of the Phorusrhacidae , it is the largest bird known from the Americas and one of the largest that has ever existed. The mandibule possesses a proportionally shorter, wider and higher symphysis than Physornis and Paraphysornis (e. g. Alvarenga, 1993: Fig. 1 ) The internal condyle of the tibiotarsus is medially diverted. The cotyls of the tarsometatarsus are rounded off and the mandibular symphysis (MLP-94-95), mistakenly attributed to the premaxillas by Moreno & Mercerat (1891); quadrate, several complete and incomplete thoracic and caudal vertebras, phalanges and fragments of the hindlimbs (MLP-92-93 and 96-117, Fig. 10B ); the complete left and the distal end of the right tarsometatarsus (FM-P13259, Fig. 10A ); a distal extremity of the right tarsometatarsus (BMNH-A578); distal extremity of the left tarsometatarsus (BMNH-A580); 10 podal and ungual phalanges, the majority belonging to the left foot, apparently from the same specimen (BMNH-A549, Fig. 11 ); distal end of the left femur (FM-P15309).

Horizon and Locality – Lower and Middle Miocene

(Santacrucian) of Argentina, Province of Santa Cruz: Lago Argentina, Monte Leon, Monte Observación, Kariaken, La Cueva, Rio Gallegos.

Measurements – Table 2.

Illustrations – Moreno & Mercerat (1891).

Remarks – The trochleae of the right tarsometatarsus of specimen MLP-112 ( Fig. 10B ), which Moreno & Mercerat (1891) conceived and assigned to Rostrornis floweri , is a mistaken assemblage, wherein the internal trochlea is, in fact, an external left trochlea. Such an error in assemblage also served Dolgopol de Saez (1927) to characterize the genus Rostrornis . An appreciable difference in the size of the tarsometatarsus of specimens FM-P13259 and MLP-91 (lectotype) ( Fig. 2C and 2D ), shows the second to be around 33% larger than the first, which possibly testifies to a sexual dimorphism, seeing that by the characteristics, both are adults. Two distal fragments of tarsometatarsus from the museum in London (BMNH-A578 and A580) are in accordance with this difference in size ( Table 2).

Ameghino (1895) described Brontornis platyonyx , basing it on the much smaller build than B. burmeisteri . His measurements are, however, compatible with the abovementioned variation for the species ( Fig. 11 ).

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 7. An incomplete jaw of Brontornis burmeisteri (MNHN-1902-6) in:A - dorsal view,B - lateral view and C - ventral view.

FIGURE 10. Brontornis burmeisteri: distal view of the right tarsometatarsus. A - cast of specimen FM-P13259, lacking the external trochlea; B - specimen MLP-112. Note the error in assembling (B) the “internal” trochlea (arrow), which, in fact, is the left external trochlea.This mistake,which was initially made by Moreno & Mercerat (1891), was also passed on by Dolgopol de Saez (1927), serving as a notable difference for the characterization of the genus Rostrornis.

FIGURE 11. Podal phalanges (BMNH-A549), type of Brontornis platyonyx Ameghino, 1895. The measurements and morphology are concordant with those of B. burmeisteri.