Megalolamna paradoxodon

SHIMADA, CHANDLER, LAM, TANAKA & WARD, 2017


Classification: Elasmobranchii Lamniformes Otodontidae

Reference of the original description
SHIMADA, K. & CHANDLER, R.E. & LAM, O.L.T. & TANAKA, T. & WARD, D.J. (2017)
A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene, and comments on the taxonomy of otodontid genera, including the ‘megatoothed’ clade. Historical Biology, 29 (5): 704-714

Types
Megalolamna paradoxodon
Holotype: UCMP: 112146;


Description:


Citation: Megalolamna paradoxodon SHIMADA, CHANDLER, LAM, TANAKA & WARD, 2017: In: Database of fossil elasmobranch teeth www.shark-references.com, World Wide Web electronic publication, Version 05/2021

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Description
Original diagnose after Shimada et al. (2017) p. 706 [24480]: Lamniform differing from all known species of otodontids (sensu this paper; see Discussion) by the following combination of characters: tooth consisting of a sharply-pointed, relatively tall, triangular main cusp, one prominent pair of triangular lateral cusplets, and strongly bilobed root; main cusp erect, slightly inclined distally, or gently curved distally; lingual crown face very convex without ornamentation; labial crown face flat or subtly convex except center of base with weak depression; height and width of each lateral cusplet nearly equal with tendency to point outward; both mesial and distal cutting edges of main cusp and lateral cusplets smooth and razor-like, and continuous from apex to base; main cusp and lateral cusplets nearly erect to gently curved lingually; concave crown base and distinct tooth neck on lingual face; prominent tooth neck also on labial face in tall teeth, forming rounded ledge with thin enameloid layer that grades into enameloid of main cusp and lateral cusplets; bilobed root with rounded basal tips and moderately tight basal concavity in between; root overall robust but particularly at lingual protuberance that generally exhibits one or two prominent and a few smaller nutritive foramina; root width slightly wider than total crown width; osteodentine tooth histology.

Remarks
type species of Megalolamna Shimada et al., 2016 p. 706 [24480] by original designation (Art. 68.2 ICZN);

valid after Shimada et al. (2017) p. 706 [24480];


References
CARRILLO-BRICEÑO, J.D. & VILLAFAÑA, J.A. & DE GRACIA, C. & FLORES-ALCÍVAR, F.F. & KINDLIMANN, R. & ABELLA, J. (2020)
Diversity and paleoenvironmental implications of an elasmobranch assemblage from the Oligocene–Miocene boundary of Ecuador. PeerJ, 8: e9051
DOI: 10.7717/peerj.9051
LANDINI, W. & COLLARETA, A. & DI CELMA, C. & MALINVERNO, E. & URBINA, M. & BIANUCCI, G. (2019)
The early Miocene elasmobranch assemblage from Zamaca (Chilcatay Formation, Peru). Journal of South American Earth Sciences, 91: 352-371
DOI: 10.1016/j.jsames.2018.08.004
CONDAMINE, F.L. & ROMIEU, J. & GUINOT, G. (2019)
Climate cooling and clade competition likely drove the decline of lamniform sharks. Proceedings of the National Academy of Sciences of the United States of America, 116 (41) 20584-20590
DOI: 10.1073/pnas.1902693116
SHIMADA, K. & CHANDLER, R.E. & LAM, O.L.T. & TANAKA, T. & WARD, D.J. (2017)
A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene, and comments on the taxonomy of otodontid genera, including the ‘megatoothed’ clade. Historical Biology, 29 (5): 704-714
DOI: 10.1080/08912963.2016.1236795