Hybodont sharks from the Early Cretaceous of Thailand. (original) (raw)
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Freshwater hybodont sharks from the Lower Cretaceous of Thailand
International Congress on …, 2004
The lower Cretaceous of Thailand has yielded isolated teeth of eight hybodont genera, including Hybodus, Lonchidion, Thaiodus and Heteroptychodus. They are distributed in two successive assemblages, the first one from the Sao Khua Formation (Neocomian), and the second one from the Khok Kruat Formation (Aptian), with only two genera in common between these two assemblages, Hybodus and Heteroptychodus. These sharks show a wide range of diet and many of them were restricted to freshwater environment and thus endemic to the Khorat Plateau. The distribution of Thaiodus and Heteroptychodus, known in other Asian locations, may be explained by a mode of life similar to that of the modern sawfish Pristis perotteti.
A new hybodont with a cutting dentition from the Lower Cretaceous of Thailand
Cretaceous Research, 2009
A new species of hybodont shark with a cutting dentition, Mukdahanodus trisivakulii gen. nov. et sp. nov., from the Lower Cretaceous Sao Khua Formation of Thailand is described. After a turn-over in hybodont faunas in Thailand, it was apparently replaced in the Aptian/Albian ecosystem by Thaiodus ruchae. A comparative study indicates that cutting dentitions with serrated teeth appeared four times independently within the hybodont sharks over a rather short period of time, from the Late Jurassic to the Albian. Moreover, such a dentition occurred only in species spending at least part of their life cycle in fresh waters. Two main kinds of cutting dentition can be identified among hybodonts: high-crowned (Priohybodus) and low-crowned (Mukdahanodus gen. nov., Thaiodus and Pororhiza).
Shark faunas from the Late Jurassic—Early Cretaceous of northeastern Thailand
Paläontologische Zeitschrift, 2013
A revision of the freshwater shark fauna from the Phu Kradung Formation in NE Thailand allows the recognition of a new species of Acrodus, which represents the youngest occurrence of the genus and confirms its displacement in freshwater environments after the Toarcian. The rest of the shark fauna includes teeth of Hybodus sp., aff. Hybodus sp., hybodontid dermal denticles, Jiaodontus sp., Lonchidion sp. A, Lonchidion sp. B, Heteroptychodus cf. H. kokutensis and dorsal fin spines. The presence of Jaiodontus and of unusual hybodontid dermal denticles suggests a Jurassic age for most of the Phu Kradung Formation, whereas the presence of Heteroptychodus suggests an Early Cretaceous age for the top of the Formation. However, the age of the Phu Kradung Formation is still uncertain, with contradictory signals coming from palynology, detrital zircon thermochronology and vertebrate palaeontology. In any case, it appears that this is the oldest occurrence of the genus Heteroptychodus, and suggests a Thai origin for this genus, which may have replaced Acrodus in the Thai freshwater palaeoecosystems. Together with Acrodus, the presence of Lonchidion sp. A suggests some European affinities for the shark fauna from the Phu Kradung Formation.
Hybodont sharks from the Aptian-Albian of Tunisia and Thailand
Isolated teeth of six hybodont genera, including Hybodus, Thaiodus and Heteroptychodus, are described from the freshwater Lower Cretaceous of Thailand. The presence of the South American hybodont genus Tribodus, based on isolated teeth, is reported from the Lower Cretaceous of Tunisia in a brackish or freshwater environment. The appearance during the Lower Cretaceous among hybodonts of specializations like cutting teeth (Thaiodus, Priohybodus, Pororhiza) and hyostylic jaw suspension (Tribodus) indicates that this lineage was still very successful in freshwater and brackish environments by that time. In terms of number of genera and diversity of diet, the hybodonts were more diversified during the Lower Cretaceous than during the whole Triassic. (2000). -Dinosaurs and other fossil vertebrates from fluvial deposits in the Lower Cretaceous of southern Tunisia. Palaeogeography, Palaeoclimatology, Palaeoecology, 157, 227-246.
First hybodont shark assemblage from the Cretaceous of Malaysia: updated report
A new hybodont assemblage was found in Cretaceous freshwater sediment of Peninsular Malaysia. This is the first discovery of Mesozoic nonmarine fishes from Malaysia. A faunal comparison with the Khorat Group has also been carried out. Approximately 100 specimens were prepared and examined in this study. The Malaysian material provides a finer understanding of morphological variation in the teeth of freshwater hybodont sharks from Southeastern Asia, as well as of their distribution. It points out for the first time to a biostratigraphical correlation between the Cretaceous freshwater deposits in Peninsular Malaysia with those of the Khorat Group in Thailand.
A review of the hybodont sharks from the Mesozoic of Thailand
Proceedings of the International Conference on …, 2005
We propose here a quick review of the hybodont assemblages from the Mesozoic of Thailand, both from the Indochina and Sibumasu (Shan-Thai) terranes. The faunas from the Triassic and the Jurassic are still imperfectly known. The faunas from the Cretaceous, found so far only in the Indochina terrane, represent an assemblage endemic to Asia and well adapted to life in freshwater. Current data suggest that they originated from a European stock sometimes during the Jurassic. These Thai assemblages seem also to suggest that the marine ptychodontids emerged from a freshwater lonchiidid lineage at the beginning of the Cretaceous.
2007
Abstract—We describe the morphology and histological structure of the teeth of the hybodontoid shark Lonchiodion humblei from the Upper Triassic Chinle Group in Texas and New Mexico. The five morphotypes (symphyseal, mesial, anterolateral, lateral and posterior) previously applied to the teeth of other species of Lonchidion are applicable to L. humblei, which exhibits moderate heterodonty. The histological structure of the teeth also changes slightly posteriorly through the dentition. The function of the teeth of L.
The Mesozoic fossil record of sharks in Thailand
2007
terranes, and represent at least 21 species, many of which have not yet been named, distributed in 14 genera. The vast majority of these fossils belong to hybodont sharks. Fossil remains from the Triassic are still in need of study, while the Jurassic has yielded teeth of a primitive batoid, as well as those of hybodont sharks. The Cretaceous is mostly characterized by freshwater hybodont sharks endemic to Asia. In total 30 fossiliferous sites yielding Mesozoic sharks have been recorded across the country so far.