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A new snake skull from the Paleocene of Bolivia sheds light on the evolution of macrostomatans.

Scanferla A, Zaher H, Novas FE, de Muizon C, Céspedes R - PLoS ONE (2013)

Bottom Line: The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade.Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times.This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

View Article: PubMed Central - PubMed

Affiliation: Consejo Nacional de Investigaciones Científicas Y Técnicas, Instituto de Bio y Geociencias del NOA, Museo de Ciencias Naturales de Salta, Salta, Argentina. agustin_scanferla@yahoo.com.ar

ABSTRACT
Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

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Related in: MedlinePlus

Details of the holotype specimen of Kataria anisodonta.(A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.
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pone-0057583-g002: Details of the holotype specimen of Kataria anisodonta.(A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.

Mentions: The preserved snout bones of Kataria retain a typical “booid” morphology. The vomer is remarkably long, with well-developed vertical and horizontal posterior laminae (Fig. 1B), condition present in Anilius and many macrostomatans except caenophidians [26]. A single foramen pierces the posterior wall of the cavity housing Jacobson’s organ, and the sidewall of this structure is formed largely by the septomaxilla rather than the vomer, a condition shared also with non-caenophidian snakes [26]. Contrary to the plesiomorphic condition present in basal macrostomatans, the vomeronasal cupola of Kataria is closed medially by an extensive medial contact between vomer and septomaxilla (Fig. 1B). The lateral flange of the septomaxilla is present, but somewhat crushed, and shows a broad base. The septomaxilla projects caudally to the posterior border of the vomer to form a postero-dorsally ascending flange that reaches the frontal medially. The posterior tip of the ascending flange of the septomaxilla is clearly rounded, and there are no traces of articular structures that link this bone with the frontal subolfactory process. A slight dorsal displacement of the snout complex gives the impression of a septomaxilla-frontal contact (Fig. 2). However, suspension of the snout unit probably occurred through soft tissues and/or the nasal bone (not preserved in Kataria) instead of the septomaxilla.


A new snake skull from the Paleocene of Bolivia sheds light on the evolution of macrostomatans.

Scanferla A, Zaher H, Novas FE, de Muizon C, Céspedes R - PLoS ONE (2013)

Details of the holotype specimen of Kataria anisodonta.(A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585969&req=5

pone-0057583-g002: Details of the holotype specimen of Kataria anisodonta.(A) frontal view of the partial skull; (B) dorsolateral view of the left orbit; (C) ventral view of the palatal region; (D) scanning electron microscope image of the rear maxillary region. chp, choanal process; dot, ductus for olfactory tract; ec, ectopterygoid; fr, frontal; ip, interchoanal process; mfr, medial frontal flange; mx, maxilla; mxp, maxillary process; op, optic foramen; p, parietal; pf, prefrontal; pl, palatine; plp, palatine process; po, postorbital; ps, parasphenoid; pt, pterygoid; sm, septomaxilla; v, vomer.
Mentions: The preserved snout bones of Kataria retain a typical “booid” morphology. The vomer is remarkably long, with well-developed vertical and horizontal posterior laminae (Fig. 1B), condition present in Anilius and many macrostomatans except caenophidians [26]. A single foramen pierces the posterior wall of the cavity housing Jacobson’s organ, and the sidewall of this structure is formed largely by the septomaxilla rather than the vomer, a condition shared also with non-caenophidian snakes [26]. Contrary to the plesiomorphic condition present in basal macrostomatans, the vomeronasal cupola of Kataria is closed medially by an extensive medial contact between vomer and septomaxilla (Fig. 1B). The lateral flange of the septomaxilla is present, but somewhat crushed, and shows a broad base. The septomaxilla projects caudally to the posterior border of the vomer to form a postero-dorsally ascending flange that reaches the frontal medially. The posterior tip of the ascending flange of the septomaxilla is clearly rounded, and there are no traces of articular structures that link this bone with the frontal subolfactory process. A slight dorsal displacement of the snout complex gives the impression of a septomaxilla-frontal contact (Fig. 2). However, suspension of the snout unit probably occurred through soft tissues and/or the nasal bone (not preserved in Kataria) instead of the septomaxilla.

Bottom Line: The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade.Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times.This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

View Article: PubMed Central - PubMed

Affiliation: Consejo Nacional de Investigaciones Científicas Y Técnicas, Instituto de Bio y Geociencias del NOA, Museo de Ciencias Naturales de Salta, Salta, Argentina. agustin_scanferla@yahoo.com.ar

ABSTRACT
Macrostomatan snakes, one of the most diverse extant clades of squamates, display an impressive arsenal of cranial features to consume a vast array of preys. In the absence of indisputable fossil representatives of this clade with well-preserved skulls, the mode and timing of these extraordinary morphological novelties remain obscure. Here, we report the discovery of Kataria anisodonta n. gen. n. sp., a macrostomatan snake recovered in the Early Palaeocene locality of Tiupampa, Bolivia. The holotype consists of a partial, minute skull that exhibits a combination of booid and caenophidian characters, being the presence of an anisodont dentition and diastema in the maxilla the most distinctive trait. Phylogenetic analysis places Kataria basal to the Caenophidia+Tropidophiidae, and represents along with bolyeriids a distinctive clade of derived macrostomatans. The discovery of Kataria highlights the morphological diversity in the maxilla among derived macrostomatans, demonstrating the relevance of maxillary transformations in the evolution of this clade. Kataria represents the oldest macrostomatan skull recovered, revealing that the diversification of macrostomatans was well under way in early Tertiary times. This record also reinforces the importance of Gondwanan territories in the history of snakes, not only in the origin of the entire group but also in the evolution of ingroup clades.

Show MeSH
Related in: MedlinePlus