Systematic Revision Of The Phorusrhacidae (Aves: Ralliformes) Author Alvarenga, Herculano M. F. Museu de História Natural de Taubaté. Rua Colômbia, 99, CEP 12030 - 520, Taubaté, SP, Brasil. halvarenga@uol.com.br Author Höfling, Elizabeth Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, Caixa Postal 11.294, CEP 05422 - 970, São Paulo, SP, Brazil. text Papéis Avulsos de Zoologia 2003 2003-12-31 43 4 55 91 journal article 10.1590/S0031-10492003000400001 1807-0205 4900701 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). FIGURE 9. The hypotarsal region of Brontornis burmeisteri (specimen FM-P13259) is situated on a more distal level than the articular cotylae, whereas in Physornis and Paraphysornis the proximal portion of the hypotarsus is on approximately the same level. 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. FIGURE 11. Podal phalanges (BMNH-A549), type of Brontornis platyonyx Ameghino, 1895 . The measurements and morphology are concordant with those of B. burmeisteri . 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 ).