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The first freshwater mosasauroid (Upper Cretaceous, Hungary) and a new clade of basal mosasauroids.

Makádi L, Caldwell MW, Ősi A - PLoS ONE (2012)

Bottom Line: Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments.Previous to this find, only one specimen of a marine mosasauroid, cf.Plioplatecarpus sp., is known from non-marine rocks in Western Canada.

View Article: PubMed Central - PubMed

Affiliation: Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary. iharkutia@yahoo.com

ABSTRACT
Mosasauroids are conventionally conceived of as gigantic, obligatorily aquatic marine lizards (1000s of specimens from marine deposited rocks) with a cosmopolitan distribution in the Late Cretaceous (90-65 million years ago [mya]) oceans and seas of the world. Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments. Previous to this find, only one specimen of a marine mosasauroid, cf. Plioplatecarpus sp., is known from non-marine rocks in Western Canada. Pannoniasaurus inexpectatus gen. et sp. nov. uniquely possesses a plesiomorphic pelvic anatomy, a non-mosasauroid but pontosaur-like tail osteology, possibly limbs like a terrestrial lizard, and a flattened, crocodile-like skull. Cladistic analysis reconstructs P. inexpectatus in a new clade of mosasauroids: (Pannoniasaurus (Tethysaurus (Yaguarasaurus, Russellosaurus))). P. inexpectatus is part of a mixed terrestrial and freshwater faunal assemblage that includes fishes, amphibians turtles, terrestrial lizards, crocodiles, pterosaurs, dinosaurs and birds.

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Cervical and dorsal vertebrae and first sacral vertebra of Pannoniasaurus inexpectatus.Mid-cervical vertebra (MTM V.01.149.) in left lateral (A), and ventral (B) views. Posterior cervical vertebra (MTM V.2000.19.) in anterior (C), posterior (D), and dorsal (E) views. Dorsal vertebra (MTM V.01.222.) in anterior (F), posterior (G), dorsal (H), ventral (I), and right lateral (J) views. Dorsal vertebra (MTM Gyn/114.) exhibiting precondylar constriction in dorsal (K) view. first sacral vertebra (MTM Gyn/122.) in anterior (L), posterior (M), dorsal (N), ventral (O), and left lateral (P) views. Scale bars represent 1 cm.
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pone-0051781-g006: Cervical and dorsal vertebrae and first sacral vertebra of Pannoniasaurus inexpectatus.Mid-cervical vertebra (MTM V.01.149.) in left lateral (A), and ventral (B) views. Posterior cervical vertebra (MTM V.2000.19.) in anterior (C), posterior (D), and dorsal (E) views. Dorsal vertebra (MTM V.01.222.) in anterior (F), posterior (G), dorsal (H), ventral (I), and right lateral (J) views. Dorsal vertebra (MTM Gyn/114.) exhibiting precondylar constriction in dorsal (K) view. first sacral vertebra (MTM Gyn/122.) in anterior (L), posterior (M), dorsal (N), ventral (O), and left lateral (P) views. Scale bars represent 1 cm.

Mentions: The vertebrae (Figures 4N−R, 6A−P, 7A−I) of Pannoniasaurus are similar in almost all respects (size, shape, size and shape of processes, and intracolumnar variation) to those of Tethysaurus[33], and cannot be compared to either Russellosaurus[37] or Yaguarasaurus[38], [41] as postcranial remains are almost entirely absent for both taxa. In all presacral vertebrae of Pannoniasaurus inexpectatus the condyles/cotyles are oval and oblique, and the vertebral condyles are flared ( = precondylar constriction) (most pronounced on juvenile cervicals), in contrast to all known mosasauroids [6], [43], but similar to varanids [46]. The cervicals (Figures 4N, 6A−E) have compressed centra similar to Tethysaurus and Halisaurus[33], [45], [47], and bear small zygosphenes and zygantra. Large crests extend between the synapophyses and anterior edge of the cotyles and project ventrally below the ventral surface of the centrum as in Halisaurus[47], [48] and Tethysaurus[33], and are morphologically similar to the dorsally positioned pterosphenes of palaeophiid snakes [49]. Hypapophyseal peduncles have circular articulation surfaces in contrast to Tethysaurus[33]. Zygosphenes/zygantra are small on the anteriormost dorsals, similar to the cervicals. Further posteriorly on the dorsals (Figures 4O, 6F−K) the zygosphenes/zygantra become large and functional. Contrary to the condition in Tethysaurus, no vertebrae exhibit parazygosphenal and paracotylar foramina [33]. In contrast to derived mosasauroids, i.e., taxa within the grade of hydropelvic mosasaurs [6], [43], there appear to be two sacrals. The massive first sacral (Figures 4P, 6L−P) is short and broad. The posteroventrally projecting transverse processes are crescent-shaped in cross-section and share a broad platform with the prezygapophyses. The zygosphenes of the first sacral are the largest in the vertebral series. The second sacral (Figures 4Q, 7A−E) is similar to the first in general shape but its centrum and transverse processes are less robust, the latter being subcircular in cross-section. The distal end of the transverse process bears a facet for the articulation with the ilium. Zygosphenes/zygantra are present. The caudals (Figures 4R, 7F−I) are similar to those of Tethysaurus[33] and to pontosaurs [50]. The centra are elongate, being app. two times longer than wide (width/length ratio: 1.8–2.3) with the anterior caudals being slightly shorter compared to the posterior ones. The condyles/cotyles are circular, the posteriorly directed haemapophyses are large, the haemal arches are unfused, the prezygapophyses are elongate, while the postzygapophyses are small on the neural spines, and zygosphenes/zygantra are absent. The anterior caudals bear well-developed transverse processes. The neural spines are nearly two times the length of the centra and project posteriorly. The ribs (Figures 4S, 7J) have a shape typical of mosasaurs [6], [43] and their heads heads are more oval than in Tethysaurus (LM, personal observation).


The first freshwater mosasauroid (Upper Cretaceous, Hungary) and a new clade of basal mosasauroids.

Makádi L, Caldwell MW, Ősi A - PLoS ONE (2012)

Cervical and dorsal vertebrae and first sacral vertebra of Pannoniasaurus inexpectatus.Mid-cervical vertebra (MTM V.01.149.) in left lateral (A), and ventral (B) views. Posterior cervical vertebra (MTM V.2000.19.) in anterior (C), posterior (D), and dorsal (E) views. Dorsal vertebra (MTM V.01.222.) in anterior (F), posterior (G), dorsal (H), ventral (I), and right lateral (J) views. Dorsal vertebra (MTM Gyn/114.) exhibiting precondylar constriction in dorsal (K) view. first sacral vertebra (MTM Gyn/122.) in anterior (L), posterior (M), dorsal (N), ventral (O), and left lateral (P) views. Scale bars represent 1 cm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3526648&req=5

pone-0051781-g006: Cervical and dorsal vertebrae and first sacral vertebra of Pannoniasaurus inexpectatus.Mid-cervical vertebra (MTM V.01.149.) in left lateral (A), and ventral (B) views. Posterior cervical vertebra (MTM V.2000.19.) in anterior (C), posterior (D), and dorsal (E) views. Dorsal vertebra (MTM V.01.222.) in anterior (F), posterior (G), dorsal (H), ventral (I), and right lateral (J) views. Dorsal vertebra (MTM Gyn/114.) exhibiting precondylar constriction in dorsal (K) view. first sacral vertebra (MTM Gyn/122.) in anterior (L), posterior (M), dorsal (N), ventral (O), and left lateral (P) views. Scale bars represent 1 cm.
Mentions: The vertebrae (Figures 4N−R, 6A−P, 7A−I) of Pannoniasaurus are similar in almost all respects (size, shape, size and shape of processes, and intracolumnar variation) to those of Tethysaurus[33], and cannot be compared to either Russellosaurus[37] or Yaguarasaurus[38], [41] as postcranial remains are almost entirely absent for both taxa. In all presacral vertebrae of Pannoniasaurus inexpectatus the condyles/cotyles are oval and oblique, and the vertebral condyles are flared ( = precondylar constriction) (most pronounced on juvenile cervicals), in contrast to all known mosasauroids [6], [43], but similar to varanids [46]. The cervicals (Figures 4N, 6A−E) have compressed centra similar to Tethysaurus and Halisaurus[33], [45], [47], and bear small zygosphenes and zygantra. Large crests extend between the synapophyses and anterior edge of the cotyles and project ventrally below the ventral surface of the centrum as in Halisaurus[47], [48] and Tethysaurus[33], and are morphologically similar to the dorsally positioned pterosphenes of palaeophiid snakes [49]. Hypapophyseal peduncles have circular articulation surfaces in contrast to Tethysaurus[33]. Zygosphenes/zygantra are small on the anteriormost dorsals, similar to the cervicals. Further posteriorly on the dorsals (Figures 4O, 6F−K) the zygosphenes/zygantra become large and functional. Contrary to the condition in Tethysaurus, no vertebrae exhibit parazygosphenal and paracotylar foramina [33]. In contrast to derived mosasauroids, i.e., taxa within the grade of hydropelvic mosasaurs [6], [43], there appear to be two sacrals. The massive first sacral (Figures 4P, 6L−P) is short and broad. The posteroventrally projecting transverse processes are crescent-shaped in cross-section and share a broad platform with the prezygapophyses. The zygosphenes of the first sacral are the largest in the vertebral series. The second sacral (Figures 4Q, 7A−E) is similar to the first in general shape but its centrum and transverse processes are less robust, the latter being subcircular in cross-section. The distal end of the transverse process bears a facet for the articulation with the ilium. Zygosphenes/zygantra are present. The caudals (Figures 4R, 7F−I) are similar to those of Tethysaurus[33] and to pontosaurs [50]. The centra are elongate, being app. two times longer than wide (width/length ratio: 1.8–2.3) with the anterior caudals being slightly shorter compared to the posterior ones. The condyles/cotyles are circular, the posteriorly directed haemapophyses are large, the haemal arches are unfused, the prezygapophyses are elongate, while the postzygapophyses are small on the neural spines, and zygosphenes/zygantra are absent. The anterior caudals bear well-developed transverse processes. The neural spines are nearly two times the length of the centra and project posteriorly. The ribs (Figures 4S, 7J) have a shape typical of mosasaurs [6], [43] and their heads heads are more oval than in Tethysaurus (LM, personal observation).

Bottom Line: Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments.Previous to this find, only one specimen of a marine mosasauroid, cf.Plioplatecarpus sp., is known from non-marine rocks in Western Canada.

View Article: PubMed Central - PubMed

Affiliation: Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary. iharkutia@yahoo.com

ABSTRACT
Mosasauroids are conventionally conceived of as gigantic, obligatorily aquatic marine lizards (1000s of specimens from marine deposited rocks) with a cosmopolitan distribution in the Late Cretaceous (90-65 million years ago [mya]) oceans and seas of the world. Here we report on the fossilized remains of numerous individuals (small juveniles to large adults) of a new taxon, Pannoniasaurus inexpectatus gen. et sp. nov. from the Csehbánya Formation, Hungary (Santonian, Upper Cretaceous, 85.3-83.5 mya) that represent the first known mosasauroid that lived in freshwater environments. Previous to this find, only one specimen of a marine mosasauroid, cf. Plioplatecarpus sp., is known from non-marine rocks in Western Canada. Pannoniasaurus inexpectatus gen. et sp. nov. uniquely possesses a plesiomorphic pelvic anatomy, a non-mosasauroid but pontosaur-like tail osteology, possibly limbs like a terrestrial lizard, and a flattened, crocodile-like skull. Cladistic analysis reconstructs P. inexpectatus in a new clade of mosasauroids: (Pannoniasaurus (Tethysaurus (Yaguarasaurus, Russellosaurus))). P. inexpectatus is part of a mixed terrestrial and freshwater faunal assemblage that includes fishes, amphibians turtles, terrestrial lizards, crocodiles, pterosaurs, dinosaurs and birds.

Show MeSH
Related in: MedlinePlus