Friday, March 30, 2018

[Paleontology • 2018] Mandasuchus tanyauchen • A Pseudosuchian Archosaur from the Manda Beds (?Middle Triassic) of Tanzania


Mandasuchus tanyauchen
 Butler, Nesbitt, Charig, Gower & Barrett, 2018


ABSTRACT
The diverse assemblage of extinct archosaur species known from the Manda Beds of Tanzania has provided key insights into the timing and tempo of the early part of the archosaur radiation during the Middle Triassic. Several archosaur specimens were collected from the Manda Beds in 1933 by F. R. Parrington, and three of these were subsequently described and made the basis of a new genus, ‘Mandasuchus,’ in a 1956 doctoral dissertation. However, this important fossil material was never formally published, and >60 years later ‘Mandasuchus’ and ‘Mandasuchus tanyauchen’ remain nomina nuda, despite frequent references to them in the literature. Here, we provide a detailed description of this material, provide the first formal diagnosis of Mandasuchus tanyauchen, gen. et sp. nov., and assess its phylogenetic position. The holotype of M. tanyauchen includes a well-preserved partial postcranial skeleton and fragmentary cranial remains. Four referred specimens include two partial skeletons, consisting primary of postcranial remains, a partial maxilla that was previously assigned to the dinosaur clade Saurischia, and a well-preserved astragalus and calcaneum that may belong to the holotype individual. Mandasuchus tanyauchen is diagnosed by a unique combination of character states, as well as by two possible autapomorphies (ascending process of maxilla thin and compressed from anterolateral to posteromedial; femur with distinct pit lateral to the distal-most expression of the posteromedial tuber). Our phylogenetic analysis recovered M. tanyauchen within Paracrocodylomorpha, as the sister taxon to all other sampled members of Loricata.

FIGURE 1. Reconstruction of Mandasuchus and accompanying caption commissioned for the Brooke Bond Picture Card album on ‘Prehistoric Animals’ (Charig and Wilson, 1971).
 twitter.com/ButlerLabBham 

FIGURE 27. Life reconstruction of Mandasuchus tanyauchen, gen. et sp. nov.

created by Mark Witton/Natural History Museum, London. @MarkWitton

FIGURE 3. Skeletal reconstructions showing the majority of the elements preserved in, and relative sizes of, each of the three partial skeletons referred to Mandasuchus tanyauchen, gen. et sp. nov.
A, NHMUK PV R6792; B, NHMUK PV R6793; C, NHMUK PV R6794.
Reconstructions created by Mark Witton. Scale bar equals 1 m.

SYSTEMATIC PALEONTOLOGY

ARCHOSAURIA Cope, 1869–1870
PSEUDOSUCHIA Zittel, 1887–1890
SUCHIA Krebs, 1974
LORICATA Merrem, 1820

MANDASUCHUS TANYAUCHEN, gen. et sp. nov.

‘Ein Saurischier-Rest’ Huene, 1939:65.
‘Mandasuchus longicervix’ Charig, 1956:25, pl. 1–32.
‘Mandasuchus’ Huene, 1956:453.
‘Mandasuchus’ Charig et al., 1956:215.
‘Mandasuchus’ Romer, 1966:368.
‘Mandasuchus tanyauchen’ Charig in Appleby et al., 1967:709.
‘Mandasuchus tanyauchen’ Charig, 1972:131, pl. 3.
‘Mandasuchus’ Sill, 1974:320.
‘Mandasuchus’ Krebs, 1976:75.
‘Mandasuchus tanyauchen’ Krebs, 1976:75.
‘Mandasuchus tanyauchen’ Cruickshank, 1979:170.
‘Mandasuchus’ Parrish, 1993:297.
‘Mandasuchus’ Juul, 1994:6.
‘Mandasuchus’ Gower, 2000:450.
‘Mandasuchus tanyauchen’ Gower, 2000:465.
‘Mandasuchus tanyauchen’ Gower, 2001:121, fig. 1.
‘Mandasuchus tanyauchen’ Thomas, 2004:17, figs. 2.4–2.13, 2.15–2.16, pls. 2.1–2.9.
‘Mandasuchus’ Sen, 2005:188, fig. 9F.
‘Mandasuchus’ de Ricqles et al., 2008:65, table 1, pl. 2.2.
‘Mandasuchus’ Lautenschlager and Desojo, 2011:376.
‘Mandasuchus’ Nesbitt, 2011:9.
‘Mandasuchus tanyauchen’ Nesbitt et al., 2013a:252, table 1, fig. 3.
‘Mandasuchus longicervix’ Nesbitt et al., 2014:1358, 1369.

....

Etymology— Genus name is derived from ‘Manda,’ for the Manda Beds, combined with ‘suchus,’ the Greek term for the Egyptian crocodile-headed god Sobek. The species name is derived from the Greek ‘tany-,’ meaning long, and ‘auchen,’ meaning neck. The genus and species names were created by A. J.C., with the species name intended to reference the elongate neck vertebrae.

Life Reconstruction:  A new life reconstruction, prepared by Mark Witton, is presented here (Fig. 27). The reconstruction is based on the proportions of the largest known specimen (NHMUK PV R6794), and missing body parts (primarily the skull) were based largely on the closely related taxon Prestosuchus.

  
Richard J. Butler, Sterling J. Nesbitt, Alan J. Charig, David J. Gower  and Paul M. Barrett. 2018. Mandasuchus tanyauchen, gen. et sp. nov., A Pseudosuchian Archosaur from the Manda Beds (?Middle Triassic) of Tanzania; pp. 96–121 in Christian A. Sidor and Sterling J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology. 37(6, Supplement).  DOI:  10.1080/02724634.2017.1343728   


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