Hybodont Shark Research Articles

A Description of the New Hybodont Shark Genus, Columnaodus, from the Burlington and Keokuk Limestones (Carboniferous, Mississippian, Osagean) of Illinois and Iowa, USA

A Description of the New Hybodont Shark Genus, Columnaodus, from the Burlington and Keokuk Limestones (Carboniferous, Mississippian, Osagean) of Illinois and Iowa, USA

The oldest Gondwanan record of durophagous shark Strophodus Agassiz, 1838 (Hybodontiformes) from the Kachchh Basin, western India

ABSTRACT The hybodont sharks were one of the most dominant groups of chondrichthyans during the Mesozoic. The genus Strophodus was one of the most successful hybodont sharks that covered marine to coastal, occasionally high salinity niches in the pantropical basins and had adapted an unique dentition for their durophagous diet. Although the European basins are enriched with the genus fossil record, the distribution in the Gondwana basins is scarce and patchy. The present study is the first report of the genus Strophodus from the Kachchh Basin and the oldest record from Gondwana. Three taxa are recorded here, viz. S. atlasensis, S. magnus and S. sp. from the ?Early to Middle Jurassic succession of Kachchh Basin that lived in the nearshore to an estuarine environment with abundant macrobenthic fauna, such as bivalves, brachiopods, gastropods and so on. The current study sheds light on the palaeoecology and palaeobiogeography of the genus. The new insights from the present work contribute to the poorly known chondrichthyan fauna from the Kachchh Basin and Gondwana as well.

Late Triassic–Early Jurassic continental vertebrates and their environmental context from the Junggar Basin, Xinjiang, NW China

Abstract Vertebrate assemblages from the Junggar Basin in Xinjiang, China, are the only ones known from palaeo-Arctic continental strata of Late Triassic and Early Jurassic age. Here we present a preliminary description of these new assemblages, focusing on the underappreciated Arctic palaeolatitude and winter freezing of this coal-bearing sequence. Mostly collected during NIGPAS-led stratigraphic studies in the 2016–17 field seasons, new assemblages include: (1) small to large sculptured palaeonisciform cranial elements and scales, small associated palaeonisciforms, a sauropterygian tooth, large-dinosaur bioturbation and additional unidentified small vertebrate bones from the Haojiagou Formation (?upper Norian–Rhaetian); (2) a medium-sized brontozoid dinosaur footprint and a previously described possible Anomoepus track from the Badaowan Formation (Hettangian–?Pliensbachian); and (3) a hybodont shark egg case of the form taxon Palaeoxyris (only the third reported from Early Jurassic age strata of China), numerous associated and fragmentary small palaeonisciform remains (including one partial skull and several small skeletons), and another possible Anomoepus track and associated dinoturbation from the Sangonghe Formation (?Pliensbachian–Toarcian). A possible ash associated with the aforementioned lower Sangonghe fish skull has produced a laser ablation inductively coupled plasma mass spectrometry age of roughly 186 Ma, consistent with a Pliensbachian age. We are optimistic that there will be many additional discoveries from early Mesozoic age strata of the Junggar Basin, the importance of which for understanding Earth system processes cannot be overemphasized.

The relationships and paleoecology of Pachystropheus rhaeticus, an enigmatic latest Triassic marine reptile (Diapsida: Thalattosauria)

ABSTRACT Pachystropheus rhaeticus is a primarily marine diapsid reptile found in Upper Triassic (Rhaetian) deposits in Britain and continental Europe. Although known for a long time, Pachystropheus remains an enigma. It was identified as the oldest choristodere based on similarities between postcranial bones and a sole cranial element. Here, we re-study all available Pachystropheus material, including new specimens, identifying all skeletal elements that are plausibly referrable to the genus. We reject some previous dubious identifications and show that reports of an ectopterygoid, the only cranial element of Pachystropheus described, were incorrect and that supposed skull elements belong to coelacanth fishes. Furthermore, we present CT data for the first time and new palynological data from Pachystropheus-bearing strata, providing a clearer picture of its stratigraphic distribution and the paleoecology of the Penarth Group. The reassessment of its phylogeny using new character informative data, places Pachystropheus as the last of the thalattosaurs, a lineage of marine reptiles abundant throughout the Triassic. We demonstrate that a specimen of Pachystropheus previously reported from the Lower Jurassic is more likely from the Late Rhaetian, and therefore the taxon does not extend across the end-Triassic Extinction. Moreover, this extends the known geological range of thalattosaurs from the Norian–Rhaetian boundary to the latest Rhaetian. Similarities in the postcranial skeleton between Pachystropheus and other askeptosauroid thalattosaurs, particularly Endennasaurus acutirostris, suggest it was able to move on land, but was most likely a primarily marine predator with an ecological niche distinct from coeval marine reptiles (placodonts, ichthyosaurs) and carnivorous fishes (hybodont sharks, actinopterygians).

A marine microvertebrate fauna from a temporary exposure of the Atherfield Clay Formation, Reigate, Surrey

A temporary exposure of the nearshore marine Atherfield Clay (Lower Greensand Formation, Aptian, Early Cretaceous) in the Reigate area (Wonham Mill) of Surrey was sampled for microvertebrate remains in Autumn 2013. Samples amounting to 858 kg of sediment were washed, dried, and sieved to 0.325 mm and the residue searched for all fossil content. This is the first definitive study of the Atherfield Clay chondrichthyan fauna of Surrey. The samples yielded teeth of hybodont sharks (Planohybodus ensis, Lonchidion breve), neoselachian sharks (Heterodontus sulcatus, Cretascyllium hassei, Protospinax sp., Protolamna sokolovi, Lamnid indet., Scyliorhinus muelleri, Scyliorhinus gen. et sp. indet., Protoscyliorhinus sp.) and batoids (Belemnobatis picteti, Squatirhina sp.). The neoselachian sharks and rays all constitute the first confident records for the various genera in the Atherfield Clay of the United Kingdom. Dermal denticles and bony fish teeth are also present in the samples, which also yielded small numbers of invertebrates (ammonite and crustacean), microcoprolites (Tomaculopsis tomaculopsis) and plant remains (fern indusia). The state of preservation of the chondrichthyan material suggests that none of the specimens are derived from older strata; the fauna is indigenous. The Surrey Atherfield Clay fauna is distinct from that recorded from the Atherfield Bone Bed on the Isle of Wight and the roughly coeval boreal fauna of the Speeton Clay.

First occurrence of hybodontid teeth in the Luoping Biota (Middle Triassic, Anisian) and recovery of the marine ecosystem after the end-Permian mass extinction

Hybodont sharks were one of the most successful chondrichthyan lineages of all time, first occurring in the Devonian and becoming extinct in the Late Cretaceous. The end-Permian mass extinction had a limited effect on hybodont sharks, but there are fewer records of hybodonts in the Triassic than in the Jurassic and Cretaceous in China. The Middle Triassic Luoping Biota (Pelsonian, Anisian) is famous as an example of complete re-establishment of a shallow marine food web after the end-Permian mass extinction. Actinopterygian fishes are abundant and diverse in this assemblage, with 31 taxa described, including Halecomorphi and Ginglymodii. However, we still know very little about chondrichthyan fishes. Here we describe three taxa of hybodontid sharks based on teeth for the first time. One of them is ascribed to a new taxon of Lonchidiidae, Luopingselache striata gen. et sp. nov. The other two belong to Acrodus. The dentition of Luopingselache striata gen. et sp. nov. is preserved in situ and shows pronounced monognathic heterodonty. This represents the first detailed account of hybodont dentition with information of tooth replacement rate from the Mesozoic of China. We show that the tooth replacement rate is very rapid, namely 2.6 days/row on average. This rapid dental replacement rate might be an adaptation to replace broken teeth and insure the maintenance of an adequate dentition. Further, the newly discovered heterodont Luopingselache and the durophagous Acrodus sp. A and B not only made the food web more complex, but also emphasized the recovery of the marine ecosystem in the Middle Triassic after the end-Permian mass extinction.

Geology and microvertebrate faunas of the Rhaetian Westbury Formation of Doniford Bay, Somerset

The Rhaetian (latest Triassic) succession of Doniford Bay, North Somerset has been noted as a site of fossils for over 200 years, and yet has never been described in detail despite its importance for palaeontology, for knowledge of a classic Triassic-to-Jurassic transition sequence, for structural geology, and as a venue for field trips. There are two bone beds, which differ substantially in sedimentary and palaeontological characteristics. Fossils include the usual teeth, denticles, and scales of small hybodont sharks, bony fishes, and marine reptiles. The lower (basal) bone bed is in many ways like those from other localities around Bristol and in South Wales, whereas the upper bone bed shows rich organic matter and an absence of calcite, suggesting a deeper location of deposition. Further, the lower bone bed contains abundant abraded silica grains, suggesting transport of sediment and bone debris from a beach or river. The two bone beds differ in faunal composition, and the upper bone bed lacks the locally derived clasts, larger silica grains, and calcite seen in the lower bone bed. Bones and teeth are equally abraded in both bone beds, confirming long-distance transport of fish and reptile fossils and that the upper bone bed cannot be interpreted as having derived from the lower.

Hybodontiform sharks from Middle Triassic Chang 7 Member of the Ordos Basin, Shaanxi, North China: palaeobiological and palaeoecological significances

The lacustrine ecosystem of the early Ladinian of Chang 7 Member of Yanchang Formation in the Ordos Basin (Shaanxi, North China) was proposed as the earliest known Mesozoic-type, trophically multileveled lacustrine ecosystem after the end-Permian mass extinction (EPME). However, the speculated top predator shark was a mere conjecture from coiled coprolites. Herein, thirty-one shark teeth from the organic-rich mudstones of the Chang 7 Member at the Bawangzhuang section, Tongchuan City, Shaanxi Province, North China are described in detail. Two taxa of hybodontiformes, Hybodus? youngi and Hybodus sp., are identified. Based on new material and a re-examination of original material, the previously described Hybodus youngi is substantially revised by adding several newly recognized anatomical features that include flared lateral cusplets, orthodont crown with a pulp cavity surrounded by numerous dentine tubules and a monognathic heterodonty. The results indicate that at least two different hybodont sharks, associated with Saurichthys of ca. 1 m in total length, occupied the higher trophic levels of the Chang 7 Member’s lacustrine ecosystem. The re-establishment of large predator niches encompassing diverse large predators with multiple dietary habits further supports the full recovery of the lacustrine ecosystem structure 10 Myr after the EPME.

A small assemblage of marine hybodont sharks from the Bathonian of the Jaisalmer Basin, India

A small assemblage of marine hybodont sharks from the Bathonian of the Jaisalmer Basin, India

Hybodont sharks from the Jurassic of Jaisalmer, western India

ABSTRACT Jurassic (Bathonian-Oxfordian) hybodont sharks are described for the first time from the Jaisalmer Basin of Rajasthan, western India. Isolated, possibly associated, crushing-type hybodont teeth recovered from the Jaisalmer Formation (Fort, Badabag and Jajiya members) are assigned to two species of Strophodus: Strophodus jaisalmerensis sp. nov. and Strophodus sp. Strophodus, long considered to be a junior synonym of the iconic ninteenth century genus Asteracanthus, has recently been shown to be distinct from the latter. This is the first record of Strophodus from the Indian subcontinent and it significantly expands the distribution of this genus in the Jurassic of the eastern Tethys. The hybodont-bearing horizons yielded an assemblage of vertebrates (e.g. pycnodont fishes, crocodilians), invertebrates and fossil wood, suggesting a near-shore marine environment for the new species.

3D imaging of shark egg cases (Palaeoxyris) from Sweden with new insights into Early Jurassic shark ecology

ABSTRACT Several shark species produce egg cases as protective casings in which their embryos develop. These casings are composed of multiple layers of collagen and are extremely durable, making them prone to fossilisation. Here we document Palaeoxyris (Spirangium) ‒ fossil shark egg cases from Lower Jurassic successions of southern Sweden. We present high-resolution 3D images of Palaeoxyris based on microfocus X-ray computed tomography (μCT) of seven specimens, including fossils that were embedded within a sandstone matrix. Our examination of the internal structure of the egg cases revealed the possible remnants of a yolk and foetus in one specimen. The cases were most likely produced by hybodont sharks, as outlined in previous studies, and the occurrence of hybodont teeth from Lower Jurassic successions of Sweden support this. Palynological analysis of the matrix from one of the specimens hosting Palaeoxyris, indicates an early Hettangian age. The high percentage of spores (c. 60%) reveals that the egg cases were laid during the Transitional Spore Spike Interval following the end-Triassic mass extinction. The egg cases are found in conjunction with fossil horsetails; with the broader palynological and sedimentological evidence, this suggests an estuarine depositional setting, and potentially indicates that newborn sharks were living in habitats comparable to modern mangroves, as is often the case today.

Jurassic neoselachian sharks from the Mt Nerone Pelagic Carbonate Platform (Umbria-Marche Apennine, Italy): a further constrain for the palaeoecology related to PCP systems

ABSTRACT The Mt Nerone area hosts a Jurassic-Cretaceous Pelagic Carbonate Platform (PCP)-basin succession in the Umbria-Marche Domain (Central Italy). Despite being studied thoroughly on sedimentological and geological aspects, wide-spectrum palaeocological studies are currently missing for this peculiar setting. While several studies on the invertebrate fauna of PCP system are available, the vertebrate fauna remained for a long time mostly unknown. Recently a renewed interest has been directed to vertebrate remains of the region. To date, an articulated dentition and some other tooth fragments of hybodont sharks and neoginglymodian actinopterygians have been described from the Jurassic of the Mt Nerone area. These taxa indicate the existence of diverse durophagous ecological niches available for durophagous fauna in the PCP system, linked to the abundant hard-shelled invertebrate fauna inhabiting the structural highs. In the present contribution we report and describe remains of neoselachians Synechodontiformes from five localities of the Mt Nerone area. The new material, represented by several isolated teeth and referred to as Sphenodus spp., testifies an additional trophic level for the Jurassic palaeoecology in the Umbria-Marche Domain, throwing new light on the peculiar PCP-basin ecosystem.

Charles Moore and Late Triassic vertebrates: history and reassessment

Ilminster-born Charles Moore (1815-1881) was an indefatigable West Country geologist who made significant and wide-ranging contributions to the science, both in terms of the material he collected and his publications. Following his permanent move to Bath in 1853, Moore collected extensively in Late Triassic rocks, amassing a rich haul of fossil vertebrate specimens. A pioneer of bulk sampling, his fossil vertebrate collection from the Rhaetian fissure infills at Holwell, Somerset has provided much research material for subsequent study; Holwell is now the type locality for several Late Triassic mammaliaforms, reptiles (lepidosaurs) and chondrichthyans. His collection of vertebrate remains from the Arden Sandstone Formation (Carnian Age) at Ruishton has never been fully described, but contains some significant material including isolated xenacanth and hybodont shark's teeth, dorsal fin spines and cephalic spines. The objective of this present paper is to raise the profile of Moore's work on late Triassic vertebrate fossils, to highlight his innovative approach to bulk collecting, and to assess the scientific importance of his collections in both historical and modern contexts.

Microvertebrates from the Wadhurst Clay Formation (Lower Cretaceous) of Ashdown Brickworks, East Sussex, UK

Ashdown Brickworks, near Bexhill, East Sussex, has produced a large number of vertebrate fossils from the Wadhurst Clay Formation, part of the Wealden Supergroup (Hastings Group; Valanginian; Lower Cretaceous). Here we describe the microvertebrate fauna of the ‘conglomerate bed’, representing a rich sample of taxa. While most of the recovered teeth and bones are abraded, some heavily, most can be identified to species level. The taxa include four species of hybodont sharks (Egertonodus basanus, Planohybodus ensis, Polyacrodus parvidens, P. brevicostatus), three taxa of bony fishes (an unidentified Lepidotes-like semionotiform, the pycnodontiform Ocloedus, and an albuliform), three taxa of crocodyliforms (the goniopholid Hulkepholis, a bernissartiid, and the atoposaurid Theriosuchus), and the theropod dinosaurs Baryonyx and an allosauroid. Sediments of the Wadhurst Clay Formation as a whole indicate freshwater to very slightly brackish-water environments of deposition, and the mainly aquatic time-averaged mixture of fishes and tetrapods recovered from the ‘conglomerate bed’, together with isolated terrestrial species, confirms this interpretation.

A new large Late Cretaceous lamniform shark from North America, with comments on the taxonomy, paleoecology, and evolution of the genus Cretodus

ABSTRACTWe describe a partial skeleton of the Late Cretaceous shark, Cretodus, collected from the Blue Hill Shale (middle Turonian) in north-central Kansas, U.S.A. It consists of 134 disarticulated teeth, 61 vertebrae, 23 placoid scales, and fragments of calcified cartilage. The scale morphology suggests that Cretodus was a rather sluggish shark, and the vertebral morphology affirms its placement into Lamniformes. With a strong tendency towards monognathic heterodonty, the dental morphology indicates that the specimen belongs to a new species, C. houghtonorum, sp. nov., increasing the total known species of Cretodus to five. The five species can be divided into three distinct groups: the longiplicatus/semiplicatus-grade, gigantea/houghtonorum-grade, and crassidens-grade. Cretodus, that successively evolved by broadening the tooth crown. The individual of C. houghtonorum, sp. nov., is estimated to be about 515 cm in total length (TL). Our vertebra-based growth analysis suggests that the shark was about 118 cm TL at birth and that the species had an estimated maximum growth length of 684 cm TL. The large size at birth indicates that the intrauterine cannibalism behavior of embryos seen in extant lamniforms had already evolved by the Late Cretaceous. Where C. houghtonorum, sp. nov., preferred nearshore environments, the specimen co-occurred with isolated teeth of Squalicorax and fragments of two dorsal fin spines of a hybodont shark, circumstantially indicating that the individual of Cretodus fed on the much smaller hybodont and was scavenged by Squalicorax.

First remains of Lepisosteiformes actinopterygians from the Jurassic of Monte Nerone area (Umbria-Marche Apennine, Italy)

Since the early nineteenth century, the structural high of Mt. Nerone in the Umbria-Marche Sabina Domain (UMS – Central/Northern Apennines, Italy) attracted scholars from all over Europe due to the wealth of fossil fauna preserved in a stunningly well-exposed Mesozoic sedimentary succession. Several geopalaeontological studies were focused on the abundant and diverse invertebrate fauna, whereas contributions dealing with Mesozoic vertebrates were to date virtually lacking. Recently, the first material referable to hybodont sharks, consisting of an articulated crushing dentition, was described from the area and referred to Asteracanthus cf. A. magnus. In this contribution, we report the first evidence of ginglymodians actinopterygians from the Upper Jurassic of Mt. Nerone. The material is represented by seven highly tritorial isolated teeth collected from three classic fossiliferous localities of the area (i.e. Pian del Sasso, Fosso Pisciarello, I Ranchi). The general morphology of the material under study allow us to conservatively refer the teeth to the Neoginglymodi, a clade formed by Lepisosteiformes and Semionotiformes. The occurrence of durophagous organisms, to date represented by hybodont sharks and lepisosteiformes fishes, reveals interesting palaeoecological scenarios characterizing the pelagic carbonate platform-basin system of Mt. Nerone, which were most likely triggered by large-scale geodynamic processes. The complex submarine palaeotopography, inheritance of the Western Tethys Early Jurassic rifting, aroused the establishment of new infaunal and epifaunal communities opening up unexplored trophic niches for durophagous predators. The particular geodynamic setting of the UMS Domain, consisting of predominantly interconnected structural highs and lows, and the relative evolution of a diverse invertebrate fauna characterized by terebratulid, ostreids, limids, brachiopods, crustaceans, and gastropods, attracted both hybodontids anddurophagous ginglymodians in the Tethyan Realm, influencing their dispersal during the Late Jurassic.

First Cretaceous fish fauna from Malaysia

ABSTRACTCretaceous fish fossils are reported from Malaysia for the first time. They were found with dinosaur and turtle remains in nonmarine sediments in the interior of Pahang State, Peninsular Malaysia. This fish assemblage consists mostly of isolated teeth, with minor amounts of noncranial remains, including vertebral centra, scales, coprolites, and hybodont fin spines. Over 100 fish teeth were examined. Nine taxa were confirmed from this fish assemblage: six (identified and unidentified) species of hybodont sharks, Heteroptychodus kokutensis, Isanodus paladeji, Lonchidion aff. khoratensis, Mukdahanodus aff. trisivakulii, Egertonodus sp., and Hybodontidae indet., and three species of actinopterygians (ray-finned fishes): ‘Lepidotes’ sp., Halecomorphi indet., and Ginglymodi indet. This fish assemblage has strong affinities with Early Cretaceous (Barremian–early Aptian) faunas of Thailand, because the four hybodont species, H. kokutensis, I. paladeji, L. khoratensis, and M. trisivakulii, were previously known only from the Sao Khua Formation (Khorat Group) and equivalent strata of Ko Kut (Kut Island). Egertonodus has been confirmed in Asia for the first time. Overall, this fish assemblage shows a close linkage to Early Cretaceous (Barremian–early Aptian) faunas of Thailand. Based on faunal composition and biostratigraphic correlation, we suggest a Barremian–early Aptian age for this new fauna from Malaysia.

Hybodont dentition from the Upper Jurassic of Monte Nerone Pelagic Carbonate Platform (Umbria‐Marche Apennine, Italy) and its ecological implications

Here we describe a number of articulated teeth of a hybodont shark from Upper Jurassic deposits of the Monte Nerone Pelagic Carbonate Platform, in the Umbria‐Marche‐Sabina Palaeogeographic Domain (Northern Apennines, Central Italy). The material has been referred to asAsteracanthuscf.A. magnus, a quite well‐known taxon already reported from Middle to Upper Jurassic deposits of Europe. Teeth indicate an extreme crushing feeding behaviour, suggesting as putative prey both infaunal and epifaunal hard‐shelled invertebrates dwelling the sea‐floor, such as large bivalves, brachiopods, gastropods as well as vagile crustaceans. The finding represents, to date, the first formal report of hybodont shark in the Umbria‐Marche‐Sabina Domain, throwing further light on the ecology within Pelagic Carbonate Platform settings, and on the occurrence ofAsteracanthusin the Late Jurassic of the Western Tethys.

First report of hybodont shark from the Toarcian Rosso Ammonitico Formation of Umbria-Marche Apennine (Polino area, Terni, Central Italy)

In this contribution we present the first material referable to hybodont shark from the Rosso Ammonitico Formation (Umbria-Marche-Sabina Palaeogeographic Domain). Two teeth were recovered isolated within Toarcian red marly-limestone (Bifrons Zone). The best-preserved tooth is characterized by a general structure well in accord with the classic crushing dentition typical of hybodont sharks within the Subfamily Acrodontinae. The gently domed occlusal surface of the tooth does not show any trace of occlusal crest and of wrinkles, and is characterized by densely pitted, finely reticulated ornamentation. The available characters allow a conservative classification of the material at the genus level as Asteracanthus sp. The best-preserved tooth can be referred to the most mesial area of the first row of lateral teeth, using as a reference the holotype of Asteracanthus medius. The new material represents the earliest evidence of Asteracanthus and the second one from the whole Northern Apennines (Central Italy), throwing new light on the dispersal of the genus on the Jurassic Tethys.

A new hybodont shark (Chondrichthyes, Elasmobranchii) from the Upper Triassic Tiki Formation of India with remarks on its dental histology and biostratigraphy

AbstractA new lonchidiid genus,Pristrisodus, from the Upper Triassic Tiki Formation of India is described based on multiple, well-preserved, isolated teeth. Comparative analysis resulted in synonymizingParvodus tikiensisandLissodus duffini,which are known from the same horizon and resulted in a new taxon,Pristrisodus tikiensisn. comb. These teeth are elongated with mesiodistal length greater than or equal to twice the labiolingual width and have a high principal cusp, lateral cusplets, a distinct ridge near the crown-root junction labially and higher up on the crown lingually, weak ornamentation, and linear depression along the crown-root junction. Five morphotypes based on overall shape, robustness and crown height are determined. The teeth show a gradual monognathic heterodonty. The anterolateral teeth (morphotypes I−II) have high, pyramidal principal cusp with two or three small but pointed cusplets, and triangular labial and lingual protuberance. The posterolateral teeth (morphotypes III−IV) have four incipient cusplets, relatively low principal cusp, bilobed/rounded, hanging labial and incipient lingual protuberances. Morphotype V comprises anterior teeth that are broad, triangular and robust, and have rounded/blunt principal cusp, one cusplet, and low, hanging labial peg. Multivariate analyses corroborate the qualitative assessment of the Indian hybodonts. Dental histology ofPristrisodusn. gen., shows that it is distinctly different from other lonchidiid genera. The assemblage of freshwater sharks, along with other vertebrate microfossils of the Tiki Formation, shows similarity with that of the lower Tecovas Formation of the Chinle Group, USA. The euryhaline nature resulted in the adaptation of the hybodonts to freshwater systems in India during the Carnian.