Lakotemys australodakotensis, Joyce & Rollot & Cifelli Correspondence, 2020

Joyce, Walter G., Rollot, Yann & Cifelli Correspondence, Richard L., 2020, A new species of baenid turtle from the Early Cretaceous Lakota Formation of South Dakota, Fossil Record 23 (1), pp. 1-13 : 3-7

Lakotemys australodakotensis gen. et sp. nov.

Type specimen

OMNH 67133 , a partial shell ( Figs. 2 , 4a ) .

Type locality and stratum

OMNH locality V1332 , Dick Canyon, Fall River County, South Dakota (more detailed locality information is on file at OMNH); Unit 2, Chilson Member , Lakota Formation, Berriasian – Valanginian (see Geological settings above) .

Nomenclatural acts

This publication and its nomenclatural acts were registered at ZooBank on 12 February 2020, prior to publication. The LSID of the publication is urn:lsid:zoobank.org:pub:66C2A3D5-1E5C-42E8-8137-9B6253ACDA25 , that of the new genus urn:lsid:zoobank.org:act:85E563EB-2F61-4560-8DB1-11F59261825E , and that of the new species urn:lsid:zoobank.org:act:00A9D083-7874-4022-AB3C-41B9FF71841E .

Diagnosis

Lakotemys australodakotensis gen. et sp. nov. can be diagnosed as a representative of Paracryptodira by the presence of a finely sculptured skull and shell and the likely location of the foramen posterius canalis carotici interni midline along the contact of the basisphenoid and pterygoid and as a representative of Baenidae by the absence of epiplastral processes and the development of well-developed axillary and inguinal buttresses. Among named Early Cretaceous baenids, Lakotemys australodakotensis can be differentiated from Protobaena wyomingensis and Trinitichelys hiatti by having an irregularly shaped vertebral V that does not lap onto neural VIII and that forms two anterolateral processes that partially hinder vertebral IV from contacting pleural IV and can be differentiated from Arundelemys dardeni and Trinitichelys hiatti by having a broader skull and triturating surfaces (see Discussion for additional differences).

Etymology

The compound word Lakotemys is derived from the combination of the word Lakota , in reference to the indigenous Lakota people of the greater Black Hills region, and the fossil-bearing Lakota Formation , and emys, ancient Greek for turtles. The species epithet australodakotensis is formed in allusion to the state of South Dakota through the combination of the word auster with the suffix - alis, Latin for south, and Dakota. The suffix - ensis is used to indicate a location.

Referred material

OMNH 66106 , a poorly preserved skull collected from the type locality ( Fig. 3 ) ; OMNH 63615 , a poorly preserved shell collected from OMNH site V1382 ( Fig. 4 ). All referred material originates from Unit 2 of the Chilson Member of the Lakota Formation.

Figures

Figure 2. OMNH 67133, a partial shell, holotype, Lakotemys australodakotensis gen. et. sp. nov., Berriasian–Barremian Lakota Formation, Fall River County, South Dakota, USA. Photographs and illustrations in (a) dorsal and (b) ventral view. Dashed lines connote sutures observed in 3-D-rendered CT scans (see Fig. 4). Abbreviations are as follows: Ab: abdominal scute; An: anal scute; co: costal; Fe: femoral scute; Hu: humeral scute; hyo: hyoplastron; hyp: hypoplastron; Ma: marginal scutes; mes: mesoplastron; ne: neural; Pe: pectoral scutes; per: peripheral; Pl: pleural scutes; sp: suprapygal; Ve: vertebral scute; xi: xiphiplastron.

Figure 3. OMNH 63615, a partial shell, Lakotemys australodakotensis gen. et. sp. nov., Berriasian–Barremian Lakota Formation, Fall River County, South Dakota, USA. Photographs and illustrations in (a) dorsal and (b) ventral view. Dashed lines connote sutures observed in 3-D-rendered CT scans (see Fig. 4). Abbreviations are as follows: Ab: abdominal scute; co: costal; ent: entoplastron; epi: epiplastron; Ex: extragular scute; Fe: femoral scute; Gu: gular scute; Hu: humeral scute; hyo: hyoplastron; hyp: hypoplastron; IM: inframarginal scute; Ma: marginal scutes; mes: mesoplastron; ne: neural; nu: nuchal scute; Pe: pectoral scutes; per: peripheral; Ve: vertebral scute.

Figure 4. The 3-D-rendered CT images of shells, Lakotemys australodakotensis gen. et. sp. nov., Berriasian–Barremian Lakota Formation, Fall River County, South Dakota, USA.Dorsal and ventral views of (a) OMNH 67133, the holotype, and (b) OMNH 63615.Abbreviations are as follows: co: costal; ent: entoplastron; hyo: hyoplastron; hyp: hypoplastron; mes: mesoplastron; ne: neural; per: peripheral; sp: suprapygal; xi: xiphiplastron.