A new <i>Eocaiman</i> (Alligatoridae, Crocodylia) from the Itaboraí Basin, Paleogene of Rio de Janeiro, Brazil

<div><p>A new small species of <i>Eocaiman</i> is described on the basis of three anterior left mandibular rami and one isolated tooth. The specimens came from the middle-upper Paleocene Itaboraí Basin (Rio de Janeiro State, Brazil; Itaboraian South American Land Mammal Age). The new taxon differs from the other two <i>Eocaiman</i> species, such as its small size, likely participation of the splenial in the mandibular symphysis, a reduced angle between the longitudinal axis of the symphysis and the mandibular ramus, and enlarged ninth and tenth dentary teeth (in addition to the large first and fourth dentary teeth). The participation of the splenial in the mandibular symphysis is a unique character among caimanines (with the only possible exception being <i>Tsoabichi greenriverensis</i>). The new taxon provides new information on the taxonomic and anatomical diversity of the genus <i>Eocaiman</i>, a taxon of prime importance to understand the evolutionary origins of caimans given its position as the basalmost member of Caimaninae. Furthermore, the new taxon has a relatively small body size in comparison with other species of <i>Eocaiman</i>, a case paralleled by other Itaboraian reptilian groups (e.g. snakes), suggesting that this ecosystem provides critical data to test the relationship between reptilian body size and climate. </p> <p> </p> <p><a href="http://zoobank.org/83636F22-D121-4A77-9141-BE68987B6CBF" target="_blank">http://zoobank.org/83636F22-D121-4A77-9141-BE68987B6CBF</a></p> </div

Cross-section of correlation of vertical profile composites of the Bauru Group.

<p>Showing the sequence stratigraphic framework at facies association level of the Bauru Group.</p

Details of the lingual crown surfaces, showing multicrenulate longitudinal ridges, from <i>Roxochampsa paulistanus</i> comb. nov. specimens.

<p>A- DGM 259-R; B- d12 of UFRJ-DG 451-R; C- d12 of UFRJ-DG 501-R. Each scale bar = 1 mm.</p

<i>Roxochampsa paulistanus</i> comb. nov. UFRJ-DG 451-R, d12 multicrenulate tooth features.

<p>A- detail of the basal region, showing multicrenulated high relief enamel ridges; B- detail of apical region, showing granulated protuberances “scaly-forms”; C- detail of mid-apex region, showing overlapping projections; D- section of distal and crenulated carena. Scale bar for the tooth = 10 mm; in A, C and D scale bars = 1 mm; in B scale bar = 0.1mm.</p

Set up of the micro CT-scan scanning conditions.

<p>Set up of the micro CT-scan scanning conditions.</p

Geological map of the Bauru Group, Paraná Basin (modified from [104]).

<p>The outcrops that yielded Itasuchidae specimens is located with the crocodile outlines. A-B and C-D are regional geological sections.</p

New stratigraphic chart of cretaceous of the Paraná Basin.

<p>Proposition of a revised chrono-lithostratigraphy of the Bauru Group.</p

<i>Roxochampsa paulistanus</i> comb. nov. (UFRJ-DG 451-R).

<p>A- lateral view; B- medial view; C- oclusal view; D- anterior view; E- posterior view. Each scale bar = 10 mm. Legend in text.</p

Calibrated strict consensus tree from 225 MLTs (1520 steps, CI = 0.304 and RI = 0.692).

<p>The phylogenetic relationships (thin lines) come from the strict consensus tree calibrated with the geological ages (chronostratigraphic chart). Thick lines represents the species temporal range based on specimens occurrence. Also, colors in thick lines represent the inferred habit for studied species.</p

<i>Roxochampsa paulistanus</i> comb. nov. (UFRJ-DG 501-R).

<p>A- lateral view; B- medial view; C- detail, mesio-lingual surface view of tenth hemimandibular tooth; D- detail, lingual surface view of twelfth hemimandibular tooth; E- oclusal view; F- isolate tooth: a- lateral profile; b-lingual view; c- labial view. Each scale bar = 10 mm. Legend in text.</p