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. 2010 Feb 24;5(2):e9333.
doi: 10.1371/journal.pone.0009333.

A new horned crocodile from the Plio-Pleistocene hominid sites at Olduvai Gorge, Tanzania

Christopher A Brochu  1 , Jackson Njau, Robert J Blumenschine, Llewellyn D Densmore
Affiliations

A new horned crocodile from the Plio-Pleistocene hominid sites at Olduvai Gorge, Tanzania

Christopher A Brochu et al. PLoS One. .

Abstract

Background: The fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular "horns" over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus.

Methodology/principal findings: The holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma), in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus.

Conclusions/significance: The new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Cranial remains of NNHM-OLD-1001, holotype, Crocodylus anthropophagus, preserving features diagnostic of the species.
Right premaxilla in medial (A), ventral (B), dorsal (C), and lateral (D) view; partial left squamosal in dorsal (F), posterior (G), and lateral (H) view; left lacrimal in dorsal view (J); frontal with adjoining parts of prefrontals in dorsal (K) and left lateral (L) view. Specimens are compared with Crocodylus niloticus (KNM OR44, E; AMNH 7136, right side reversed, I; KNM OR54, M). Scale = 1 cm.
Figure 2
Figure 2. Craniomandibular remains of NNHM-OLD-1001, holotype, Crocodylus anthropophagus.
A, partial left nasal, dorsal view; B, right quadratojugal, lateral view; C, right jugal, lateral view; D, left jugal, lateral view; E, left jugal, medial view; F, right otic region and quadrate ramus, lateral view; G, left quadrate ramus, dorsal view; H, left quadrate ramus, ventral view; I, left quadrate ramus and paroccipital process, posteromedial view; J, braincase, posterior view; K, right pterygoid wing, ventral view; L, left pterygoid wing, ventral view; M, right ectopterygoid, ventral view; N, left ectopterygoid, ventral view; O, right postdentary bones, lateral view; P, left quadrate, dorsal view; Q, left surangular, medial view; R, fragment of dentary; S, left surangular, lateral view. Scale = 5 cm.
Figure 3
Figure 3. Postcranial remains of NNHM-OLD-1001, holotype, Crocodylus anthropophagus.
A, atlas intercentrum, anterior view. B, axis centrum and odontoid process, right lateral view. C, cervical vertebra, right lateral view. D, dorsal osteoderm, posterior view. E, dorsal osteoderm, dorsal view. F, proximal half of left humerus, ventral view. G, left ilium, medial view. H, metapodial, dorsal view. Scale = 5 cm.
Figure 4
Figure 4. Cranial remains referred to Crocodylus anthropophagus.
KNM CROC K OLD 62: anterior end of rostrum, dorsal (A) and ventral (B) view; partial frontal with portions of prefrontals in dorsal (C) and anterior (D) view; right otic region and quadrate ramus, lateral view (E). KNM FLKNI: partial orbital region, dorsal view (F); left maxilla, ventral view (G); right maxilla, medial (H), lateral (I), ventral (J), and dorsal (K) view; right squamosal, posterior (L), dorsal (M), and lateral (N) view. NHM R.5893: orbital region, dorsal view (O); partial right maxilla, ventral view (P); partial right maxilla and ectopterygoid, ventral view (Q); partial palatines and pterygoids, ventral view ( R); partial right jugal, lateral (S) and medial (T) view. Scale = 5 cm.
Figure 5
Figure 5. Partial braincase and left quadrate ramus of KNM FLKNI, Crocodylus anthropophagus, in medial (A), dorsolateral (B), and posterior (C) view.
Scale = 5 cm.
Figure 6
Figure 6. Mandibular remains referred to Crocodylus anthropophagus.
KNM BKII OLD 1960: left postdentary bones and posterior end of dentary, medial (A) and lateral (B) view; KNM FLKNI, dentaries and portion of right splenial, dorsal view (C); NHM R.5893, left dentary and splenial, medial (D) and lateral (E) view. Scale = 5 cm.
Figure 7
Figure 7. Postcranial material referred to Crocodylus anthropophagus.
A, KNM DK I B, left scapula, lateral view; B, NHM R.5894, ?nuchal osteoderm; C, KNM DK I B OLD 62 54, right humerus, ventral view; D, KNM FLKNI, right femur, ventral view. Scale = 5 cm.
Figure 8
Figure 8. Phylogenetic relationships recovered by a maximum parsimony analysis of 98 morphological characters.
Adams consensus of 426 equally optimal trees (length = 225, CI excluding uninformative characters = 0.493, RI = 0.717). Dashed lines indicate lost resolution in a strict consensus of the same trees. O = Osteolaeminae, M = Mekosuchinae, T = Tomistominae. Heavy branches indicate living lineages.
Figure 9
Figure 9. Squamosal horns of living and extinct crocodylines, left lateral view.
A, AMNH 3101, Voay robustus (right lateral view, photo inverted). B, PNCZ unnumbered, Crocodylus rhombifer. C, NHM 94.6.5.53, C. niloticus. Scale = 5 cm.
Figure 10
Figure 10. Variation in the morphology of the maxillary ramus of the ectopterygoid.
All images from right side of skull in ventral view. A, NHM R.5893, Crocodylus anthropophagus, posterior end of right maxilla and partial maxillary ramus of ectopterygoid. B, KNM FLKNI, C. anthropophagus, partial right maxilla; articulation surface for ectopterygoid is preserved. C, USNM 194831, C. niloticus. D, USNM 248848, C. niloticus. E, FMNH 17157, C. niloticus. Arrow indicates cleft in maxillary ramus of ectopterygoid; questionably present in A, on medial margin of suborbital fenestra in D. Scale = 1 cm.
See this image and copyright information in PMC

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