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New material of Macranhinga ranzii (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
E. Guilherme, L. G. D. Souza, T. S. Loboda, A. Ranzi, A. Adamy, J. Dos Santos Ferreira & J. P. Souza-Filho, 2020

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

Historical Biology: An International Journal of Paleobiology. in press.
doi:10.1080/08912963.2020.1850714

ABSTRACT:
We describe a new specimen attributed to Macranhinga 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.

Enjoy,

Fred
 
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Fred Ruhe

Well-known member
Netherlands
Systematic Palaeontology


Suliformes
Sharpe, 1891
Anhingidae Reichenbach, 1849
Macranhinga Noriega 1992

Type-species: Macranhinga paranensis

Included species: Macranhinga ranzii; Macranhinga ameghinoi

Diagnosis. Just related to the pelvic girdle characters (entirely based on Diederle and Agnolin 2017): Pre-Acetabular vertebrae with corpus vertebrae very robust; ala preacetabularis ilii more vertically oriented than in Anhinga; fossa iliaca dorsalis deeply excavated and with a prominent dorsal edge; crista iliaca dorsalis slightly laterally divergent; antitrochanter very dorsally oriented; fossa renalis at the level of the foramen acetabuli ovate and with conspicuous distal processus costalis.

Macranhinga ranzii Alvarenga and Guilherme 2003

Holotype: Left femur lacking the distal end (UFAC-3640).

Paratypes: A right femur, deformed and lacking the distal end (UFAC-4034), and well- preserved right femur (UFAC-4860).

New referred material: an almost complete pelvic girdle articulated with the synsacrum (UFAC 6471).

Emended diagnosis: pelvic girdle and synsacrum elongated with a proportionally narrow postacetabular region when compared to extant Anhinga; the crista iliaca dorsalis is proportionally more elevated than any other known fossil Anhingidae; Vertex craniolateralis ilii cranial to the foramen acetabuli and medially disposed to the antitrochanter; the dorsal foramen of the acetabular vertebrae is at the level of the antitrochanter; pronounced angulation of the ventral median axis formed by the lumbosacral mass in the craniocaudal direction; Crista spinosa synsacri and crista dorsolaterales ilii extremely tall, making the dorsal surface postacetabular region deeply concave.

Horizon and Locality: The material was recovered from rocks in the Solimões Formation, here attributed to the Upper Miocene age (Latrubesse 2015), at the left margin of the Purus River, Boca do Acre Municipality, Amazonas (8° 47ʹ19” S/67° 29ʹ 55.2” W; Figure 1). The locality, named ‘Cajueiro’, is situated ninety-eight metres above the sea level, has around six metres in height, is thirty metres deep, and almost two hundred metres in length, being composed from silt clay to claystone, ferruginous and carbonate concretion and gypsum veins (Loboda et al. 2019). Its layers are sub-horizontals, without depositional marks, thirty to fifty centimetres thick, and disposed of in successively alternating levels of oxidised and non-oxidised rocks, the latter where UFAC 6471 was found. Historically, it is important to notice that this locality is reclaimed by two Amazonian indigenous cultures, the Apurinã and the Jamamadi, as belonging to their territory.

Fred

Figure 1. Dorsal view of pelvic girdle and the synsacrum of the Macranhinga ranzii (UFAC 6471). A) original material, and B) interpretative drawing. Regions closest to the plane of the photo are in lighter shades, while the darker portions represent the most distant regions; black represent the holes present in the bone. Scale bar: 5cm.

Figure 2. Right lateral view of pelvic girdle and the synsacrum of the Macranhinga ranzii (UFAC 6471). A) original material; and, B) interpretative drawing. Regions closest to the plane of the photo are in lighter shades, while the darker portions represent the most distant regions; black represent the holes present in the bone. Scale bar: 5cm.
 

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