New material of Anhingidae (Aves: Suliformes) from the upper Miocene of the Amazon, Brazil

ABSTRACT

We describe a new specimen attributed toMacranhinga ranzii, a taxon whose holotype is a left femur, being collected from rocks in the Solimões formation, Southwestern Amazon. The new material is an almost complete pelvic girdle and synsacrum (UFAC 6471), collected in a new fossiliferous locality named Cajueiro. The compatibility between the diameter of foramen acetabuli of UFAC 6471 with the caput femoris of the holotype and the synapomorphies present in the specimen allowed us to attribute it to M. ranzii and emend the diagnosis for this species. Based on three linear measurements of the pelvic girdle and the medium weight of extant Anhinga, we estimate the adult animal’s body mass at 8.6 kg. The phylogenetic inference resulted in two equally probable evolutionary hypotheses: one of them with a monophyletic Macranhinga and in the other Meganhinga chilensis as the sister clade of a Macranhinga (in part) plus Anhinga clade. In both scenarios, Macranhinga ranzii is closely related to G. kiyuensis. The morphological and myological data gained in this study enabled us to recognise Macranhinga ranzii as a proficient swimmer and diver, and consequentially a skilled fish hunter in deep waters.

KEYWORDS:

• Aves
• fossil
• synsacrum
• Anhinga
• Macranhinga ranzii
• Solimões basin

Acknowledgments

We are grateful to the Museu da Amazônia - MUSA, on behalf of its director, Dr. Ennio Candotti, for supporting the Purus River’s expedition, logistically and financially, in honour of Dra. Rosalie Benchimol, during August 2019. We would also like to thank Dr. Peter Mann de Toledo for his valuable help during the fieldwork, the Pro-Rector of Planning at UFAC, Mr. Gleyson de Sousa Oliveira, for the essential logistical support during the expedition, and Mx. Allen Saoirse Ximenes Mugarte for the ESL proofreading and editing service. LGS thanks the financial support granted to Paleo and Geohistory exhibition at Museu da Amazônia [PRONAC 183808] and the post-doctoral scholarship granted by Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM 062.00166/2020).

Disclosure statement

The authors reported no potential conflict of interest.

Additional information

Funding

This work was supported by Fundação de Amparo à Pesquisa do Estado do Amazonas – FAPEAM, Museu da Amazônia – MUSA, Programa Nacional de Apoio à Cultura – PRONAC and Universidade Federal do Acre – UFAC.