Laganosuchus maghrebensis, Sereno & Larsson, 2009

Sereno, Paul & Larsson, Hans, 2009, Cretaceous Crocodyliforms from the Sahara, ZooKeys 28 (28), pp. 1-143 : 85-87

Laganosuchus maghrebensis sp. n.

urn:lsid:zoobank.org:act:E5BCEEAD-DFEF-4EF6-AA62-110EF91FCD0F

Fig. 42

Table 14

Etymology. Maghreb, western (Arabic); - ensis (Latin), from. Named for the area where the holotype was discovered in the Kem Kem Beds of southeastern Morocco.

Holotype. UCRC PV2 ; anterior portion of the left dentary preserving four alveoli and one replacement tooth in the anteriormost tooth position ( Fig. 42 ).

Referred material. CMN 50838, anterior left dentary fragment preserving the symphyseal end and alveoli 1–3.

Type locality. Er Rachidia District, Morocco (exact locality unknown). The referred specimen ( CMN 50838) probably was found south of Erfoud ( Fig. 1A, B).

Horizon. Kem Kem Beds, upper member; Upper Cretaceous (Cenomanian), ca. 95 Mya ( Sereno et al. 1996).

Diagnosis. Metasuchian with a narrow, well defined groove on the ventral aspect of the anterior dentary immediately lateral to the splenial that arcs to the posterior aspect of the symphysis; shallow, anteriorly tapering trough on the anterior dentary just lateral to the more sharply defined groove.

Dentary. The anterior portion of the dentary is preserved in two specimens of Laganosuchus maghrebensis . Th e very rugose dentary symphysis suggests that it may have fused with maturity, and that its size, which is somewhat smaller than Laganosuchus thaumastos , may not be significant.

The more complete specimen ( Fig. 42 A-D) shows a remarkable similarity to Laganosuchus thaumastos . Both have slender U-shaped lower jaws with the symphysis restricted to the dentary, festooned alveoli with enlarged first and second teeth, and a sharply incised Meckel’s canal developed as a narrow groove. Th e teeth are also spikeshaped without recurvature or marginal ornamentation.

Several differences, however, establish L. maghrebensis as a distinct species. The dentary is narrower near the symphysis ( Fig. 42C ), lacking the internal crest that thickens the dentary in L. thaumastos ( Fig. 38B ). Th e anterior alveoli in L. maghrebensis are not procumbent or exposed in lateral view as in L. thaumastos . Likewise, an articular scar for the splenial in L. maghrebensis shows that its anterior end tapers to a narrow tip along the ventral margin ( Fig. 42B ) in contrast to the bifurcated flanges in L. thaumas- tos ( Fig. 38B ). Th e incised groove representing Meckel’s canal is located on the ventral, rather than lingual, aspect of the dentary ( Fig. 42D ).

Although crown size in the two species is very similar, the alveolus of the caniniform tooth (d4) is slightly larger than comparable measurements for d1 (Table 14), the reverse of the condition in Laganosuchus thaumastos (Table 13). L. maghrebensis , in addition, shows low fluting on the lingual aspect of the crown of the first dentary tooth ( Fig. 42E ). A comparable crown, however is not available at the anterior end of the dentary series in L. thaumastos .

Figures

Figure 38. Lower jaws of the crocodyliform Laganosuchus thaumastos gen. n. sp. n. Cast (UCRC PVC9) of the anterior portion of the left dentary and splenial (MNN IGU13). A Left lateral view. B Medial view (reversed). C Dorsal view. D Ventral view. Scale bar equals 5 cm. Abbreviations: ad1–8, alveolus for dentary tooth 1–8; asp, articular surface for the splenial; cr, crest; d, dentary; dpr, dorsal process; gr, groove (for upper teeth); Mc, Meckel’s canal; sp, splenial; vpr, ventral process.

Figure 42. Dentary fragment of the crocodyliform Laganosuchus maghrebensis gen. n. sp. n. Anterior end of the left dentary (UCRC PV2). A Left lateral view. B Medial view (reversed). C Dorsal view. D Ventral view. E Replacement tooth in first dentary alveolus in lingual view. Scale bar in A-D equals 3 cm; scale bar in E equals 1 cm. Abbreviations: ad1, 3, alveolus for dentary tooth 1, 3; afo, alveolar foramina; asp, articular surface for the splenial; d1, 4, dentary tooth 1, 4; fl, fluting; fo, foramen; Mc, Meckel’s canal; rt, replacement tooth; sym, symphysis; tasp, tip of the articular surface for the splenial.