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Journal articles on the topic 'Polycotylidae'

Author: Grafiati

Published: 5 June 2025

Last updated: 16 July 2025

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1

Fischer, V., R. B. J. Benson, P. S. Druckenmiller, H. F. Ketchum, and N. Bardet. "The evolutionary history of polycotylid plesiosaurians." Royal Society Open Science 5, no. 3 (2018): 172177. http://dx.doi.org/10.1098/rsos.172177.

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Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. Thililua longicollis from the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long neck and, as originally reported, a series of unusual cranial features that cause unstable phylogenetic relationships for polycotylids. We reinterpret the holotype specimen of Thililua longicollis and clarify its cranial anatomy. Thililua longicollis possesses an extensive, foramina-bearing jugal, a premaxilla–parietal contact and carinated teeth. Phylogenetic analyses of a new cladistic dataset based on first-hand observation of most polycotylids recover Thililua and Mauriciosaurus as successive lineages at the base of the earliest Late Cretaceous polycotyline radiation. A new dataset summarizing the Bauplan of polycotylids reveals that their radiation produced an early burst of disparity during the Cenomanian–Turonian interval, with marked plasticity in relative neck length, but this did not arise as an ecological release following the extinction of ichthyosaurs and pliosaurids. This disparity vanished during and after the Turonian, which is consistent with a model of ‘early experimentation/late constraint’. Two polycotylid clades, Occultonectia clade nov. and Polycotylinae, survived up to the Maastrichtian, but with low diversity.

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2

José, Patricio O'GORMAN, and A. OTERO Rodrigo. "Revision of the short-necked Cretaceous plesiosaurians from New Zealand." Comptes Rendus Palevol 22, no. 6 (2023): 77–90. https://doi.org/10.5852/cr-palevol2023v22a6.

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Polycotylidae Cope, 1869 is a clade of short-necked plesiosaurians that achieved a cosmopolitan distribution by the Late Cretaceous. Here, the material previously referred to Polycotylidae/Pliosauridae from the Upper Cretaceous of New Zealand is reviewed, concluding that only 2.4% and 7.7% respectively of the total plesiosaurians specimens recovered in these formations (late Campanian-early Maastrichtian Tahora Formation and Campanian-Maastrichtian Conway Formation) belong to Polycotylidae. This proportion is similar to that recorded in upper Campanian-Maastrichtian levels of the Allen, Los Alamitos and La Colonia formations, northern Patagonia (Argentina) and southernmost Chile, but contrasts with the coeval absence of polycotylids in Campanian-Santonian levels of Antarctica and central Chile. These new results improve our knowledge about the representation of Weddellian polycotylids and underline the relative scarcity of Campanian-Maastrichtian records in the Weddellia Province.

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3

Druckenmiller, Patrick S., and Anthony P. Russell. "Earliest North American occurrence of Polycotylidae (Sauropterygia: Plesiosauria) from the Lower Cretaceous (Albian) Clearwater Formation, Alberta, Canada." Journal of Paleontology 83, no. 6 (2009): 981–89. http://dx.doi.org/10.1666/09-014.1.

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The polycotylidae is a family of short-necked (pliosauromorph) plesiosaurs, with examples known from epicontinental marine deposits of every major landmass except Antarctica. Our knowledge of its diversity and distribution has increased tremendously in the last decade, with new material described from North America (Sato, 2005; Albright et al., 2007; Schumacher, 2007; Schmeisser, 2008), South America (Gasparini and de la Fuente, 2000; Salgado et al., 2007), Africa (Bardet et al., 2003; Buchy et al., 2005), and Asia (Sato and Storrs, 2000; Arkhangel'skii et al., 2007). Polycotylid diversity is greatest in the Late Cretaceous, and particularly so in the Turonian; however, knowledge of the group's initial history in the Early Cretaceous is limited to a handful of specimens from North America (Storrs, 1981; Druckenmiller, 2002) and Australia (Kear 2003, 2005).

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4

Sato, Tamaki, and Glenn W. Storrs. "An early polycotylid plesiosaur (Reptilia: Sauropterygia) from the Cretaceous of Hokkaido, Japan." Journal of Paleontology 74, no. 5 (2000): 907–14. http://dx.doi.org/10.1017/s0022336000033096.

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A partial skeleton of a short-necked plesiosaur excavated from the Upper Cenomanian of the Middle Yezo Group of Hokkaido, Japan, includes disarticulated vertebrae, the right half of the pectoral girdle, fragments of the pelvic girdle, ribs, gastralia, and gastroliths. Gastroliths are unusual in short-necked plesiosaurs. Skeletal characters indicate that the specimen belongs to the Family Polycotylidae, well known from North America, the former Soviet Republics, and possibly from New Zealand. They are rare in East Asia and hitherto unknown from Japan. Extensive ossification indicates that this specimen is an adult individual, yet it is smaller than the adult specimens of other known polycotylids. The elongated epipodial bones are a unique character of the specimen but are probably plesiomorphic. The fossil is evidence of biogeographical diversification of the family at the beginning of the Late Cretaceous.

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5

Morgan, Donald J., and F. Robin O'Keefe. "The cranial osteology of two specimens of Dolichorhynchops bonneri (Plesiosauria, Polycotylidae) from the Campanian of South Dakota, and a cladistic analysis of the Polycotylidae." Cretaceous Research 96 (April 2019): 149–71. http://dx.doi.org/10.1016/j.cretres.2018.11.027.

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6

DRUCKENMILLER, PATRICK S., and ANTHONY P. RUSSELL. "A phylogeny of Plesiosauria (Sauropterygia) and its bearing on the systematic status of Leptocleidus Andrews, 1922." Zootaxa 1863, no. 1 (2008): 1. http://dx.doi.org/10.11646/zootaxa.1863.1.1.

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Leptocleidus Andrews, 1922 is a poorly known plesiosaur genus from Lower Cretaceous successions of the UK, South Africa, and Australia. Historically, there has been little consensus regarding its phylogenetic position within Plesiosauria, largely because of its seemingly aberrant combination of a relatively small skull and short neck. As a result, a diverse array of potential sister groups have been posited for Leptocleidus, including long-necked Cretaceous elasmosaurids, Early Jurassic “rhomaleosaurs”, and Middle to Late Jurassic pliosaurids. A cladistic analysis including Leptocleidus, and a new, apparently morphologically similar specimen from Alberta, TMP 94.122.01, was undertaken to assess their phylogenetic position within Plesiosauria. A character-taxon matrix was assembled afresh, consisting of 33 operational taxonomic units sampled broadly among plesiosaurs. 185 cranial and postcranial characters used in plesiosaur phylogenetics were critically reanalyzed, of which 152 were employed in the parsimony analysis. The results indicate a basal dichotomous split into the traditionally recognized pliosauroid and plesiosauroid clades. Nested within Pliosauroidea, a monophyletic Leptocleididae was recovered, consisting of L. superstes Andrews, 1922 and L. capensis (Andrews, 1911a). In contrast to earlier suggestions, Leptocleidus neither clusters with Rhomaleosaurus, which was found to be paraphyletic, nor with large-skulled pliosaurid taxa, such as Simolestes. Rather, a sister group relationship between Cretaceous Polycotylidae and Leptocleididae was recovered, which is here named Leptocleidoidea. Although TMP 94.122.01 is superficially similar to Leptocleidus, several discrete characters of the skull nest this new taxon within Polycotylidae. Compared to other phylogenetic hypotheses of plesiosaurs, these results are more congruent with respect to the stratigraphic distribution of leptocleidoids. A classification for Plesiosauria is presented.

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7

O’gorman, José P., and Zulma Gasparini. "Revision ofSulcusuchus erraini(Sauropterygia, Polycotylidae) from the Upper Cretaceous of Patagonia, Argentina." Alcheringa: An Australasian Journal of Palaeontology 37, no. 2 (2013): 163–76. http://dx.doi.org/10.1080/03115518.2013.736788.

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8

Novas, Fernando E., Julia S. D'Angelo, José P. O'Gorman, Federico L. Agnolín, Juan M. Lirio, and Marcelo P. Isasi. "First record of Polycotylidae (Sauropterygia, plesiosauria) from the Upper Cretaceous of Antarctica." Cretaceous Research 56 (September 2015): 563–68. http://dx.doi.org/10.1016/j.cretres.2015.06.015.

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9

Gasparini, Zulma Nélida, and Marcelo De la Fuente. "TORTUGAS Y PLESIOSAURIOS DE LA FORMACIÓN LA COLONIA (CRETÁCICO SUPERIOR) DE PATAGONIA, ARGENTINA." Spanish Journal of Palaeontology 15, no. 1 (2021): 23. http://dx.doi.org/10.7203/sjp.15.1.22010.

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Se describen las tortugas y un plesiosaurio de la Formación La Colonia (Cretácico Superior) que aflora en las laderas sur del Macizo Norpatagónico. Los reptiles proceden de un área conocida como La Colonia, situada en el centro-norte de la provincia del Chubut, Argentina. La queloniofauna de la Formación La Colonia está constituida por al menos cinco taxones de Chelidae (Pleurodira) y uno de Meiolaniidae (Cryptodira). Los nuevos restos craneanos recuperados de Sulcusuchus erraini Gasparini y Spalletti, 1990 permiten referir esta especie como un plesiosaurio longirrostro de la familia Polycotylidae. Desde un punto de vista paleobiogeográfico en la Formación La Colonia convergen grupos de reptiles de distinto origen y distribución geográfica: quelonios y serpientes surgondwánicos, plesiosaurios relacionados con especies norteameric anas y terópodos gondwánicos.

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10

Arkhangelsky, M. S., A. O. Averianov, and E. M. Pervushov. "Short-necked plesiosaurs of the family Polycotylidae from the Campanian of the Saratov Region." Paleontological Journal 41, no. 6 (2007): 656–60. http://dx.doi.org/10.1134/s0031030107060093.

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11

Albright, L. Barry, David D. Gillette, and Alan L. Titus. "Plesiosaurs from the Upper Cretaceous (Cenomanian–Turonian) Tropic Shale of southern Utah, part 2: Polycotylidae." Journal of Vertebrate Paleontology 27, no. 1 (2007): 41–58. http://dx.doi.org/10.1671/0272-4634(2007)27[41:pftucc]2.0.co;2.

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12

Lazo, Dario G., and Marcela Cichowolski. "First plesiosaur remains from the lower Cretaceous of the Neuquén Basin, Argentina." Journal of Paleontology 77, no. 4 (2003): 784–89. http://dx.doi.org/10.1017/s0022336000044498.

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Plesiosaurs constitute a monophyletic group whose stratigraphical range is uppermost Triassic to uppermost Cretaceous (Brown, 1981). They were large predatory marine reptiles, highly adapted for submarine locomotion, with powerful paddle-like limbs and heavily reinforced limb girdles (Saint-Seine, 1955; Romer, 1966; Carroll, 1988; Benton, 1990). The Plesiosauria clade belongs to the Sauropterygia, which has recently been hypothesized as the sister-group of the Ichthyosauria. Together with that clade they form the Euryapsida (Caldwell, 1997). The Sauropterygia can be subdivided into relatively plesiomorphic stem-group taxa from the Triassic (Placodonts, Nothosauroids, and Pistosauroids), and the obligatorily marine crown-group Plesiosauria (Rieppel, 1999). Plesiosaurs are traditionally divided into two superfamilies: Plesiosauroidea, with usually small heads and long necks; and Pliosauroidea, with larger heads and shorter necks (Welles, 1943; Persson, 1963; Brown, 1981). Plesiosauroidea contains three families: Plesiosauridae, Cryptoclididae, and Elasmosauridae (Brown, 1981; Brown and Cruickshank, 1994). The validity of the Polycotylidae Cope, 1869, has long been questioned and its phylogenetic position among Plesiosauria debated, as many consider it to be related to the Pliosauridae or to be a sister-group of the Elasmosauridae (Sato and Storrs, 2000; O'Keefe, 2001).

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13

Schumacher, Bruce A., and James E. Martin. "Polycotylus latipinnisCope (Plesiosauria, Polycotylidae), a nearly complete skeleton from the Niobrara Formation (early Campanian) of southwestern South Dakota." Journal of Vertebrate Paleontology 36, no. 1 (2015): e1031341. http://dx.doi.org/10.1080/02724634.2015.1031341.

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14

ANGST, D., and N. BARDET. "A new record of the pliosaurBrachauchenius lucasiWilliston, 1903 (Reptilia: Sauropterygia) of Turonian (Late Cretaceous) age, Morocco." Geological Magazine 153, no. 3 (2015): 449–59. http://dx.doi.org/10.1017/s0016756815000321.

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AbstractThe site of Goulmima (south Morocco) is well known for its rich marine fauna of Turonian age (Late Cretaceous). It has yielded a large variety of invertebrates but also of vertebrate taxa, represented by actinopterygians and marine reptiles including Plesiosauria (Sauropterygia) and Mosasauroidea (Squamata). The Plesiosauria are known so far by two major clades of Plesiosauroidea: the Elasmosauridae (Libonectes atlasenseBuchy, 2005) and the Polycotylidae (Thililua longicollis, Bardet, Suberbiola & Jalil, 2003a;Manemergus angirostrisBuchy, Metayer & Frey, 2005). Here we describe a new specimen of plesiosaur found in the same outcrop, differing from those previously cited and belonging to the other large plesiosaur clade, the Pliosauroidea. Comparison of this specimen with other Plesiosauria shows that it belongs toBrachauchenius lucasiWilliston (1903), a species previously known only from the Cenomanian–Turonian stages of the Western Interior Seaway of North America and in the upper Barremian succession of northern South America (Colombia). The description of this species on a contemporaneous site of North Africa significantly expands its palaeobiogeographic distribution. This discovery confirms the affinities between marine faunas of the Western Interior Seaway and those of North Africa at this time, and also permits a better understanding of the palaeobiology of the Goulmima outcrop. A discussion about the systematical status ofPolyptychodonOwen, 1841 is also provided.

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15

Madzia, Daniel, and Andrea Cau. "Estimating the evolutionary rates in mosasauroids and plesiosaurs: discussion of niche occupation in Late Cretaceous seas." PeerJ 8 (April 13, 2020): e8941. http://dx.doi.org/10.7717/peerj.8941.

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Observations of temporal overlap of niche occupation among Late Cretaceous marine amniotes suggest that the rise and diversification of mosasauroid squamates might have been influenced by competition with or disappearance of some plesiosaur taxa. We discuss that hypothesis through comparisons of the rates of morphological evolution of mosasauroids throughout their evolutionary history with those inferred for contemporary plesiosaur clades. We used expanded versions of two species-level phylogenetic datasets of both these groups, updated them with stratigraphic information, and analyzed using the Bayesian inference to estimate the rates of divergence for each clade. The oscillations in evolutionary rates of the mosasauroid and plesiosaur lineages that overlapped in time and space were then used as a baseline for discussion and comparisons of traits that can affect the shape of the niche structures of aquatic amniotes, such as tooth morphologies, body size, swimming abilities, metabolism, and reproduction. Only two groups of plesiosaurs are considered to be possible niche competitors of mosasauroids: the brachauchenine pliosaurids and the polycotylid leptocleidians. However, direct evidence for interactions between mosasauroids and plesiosaurs is scarce and limited only to large mosasauroids as the predators/scavengers and polycotylids as their prey. The first mosasauroids differed from contemporary plesiosaurs in certain aspects of all discussed traits and no evidence suggests that early representatives of Mosasauroidea diversified after competitions with plesiosaurs. Nevertheless, some mosasauroids, such as tylosaurines, might have seized the opportunity and occupied the niche previously inhabited by brachauchenines, around or immediately after they became extinct, and by polycotylids that decreased their phylogenetic diversity and disparity around the time the large-sized tylosaurines started to flourish.

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Albright, L. Barry, David D. Gillette, and Alan L. Titus. "Plesiosaurs from the Upper Cretaceous (Cenomanian–Turonian) Tropic Shale of Southern Utah, part 2: Polycotylidae; replacement names for the preoccupied genusPalmulaand the subfamily palmulainae." Journal of Vertebrate Paleontology 27, no. 4 (2007): 1051. http://dx.doi.org/10.1671/0272-4634(2007)27[1051:pftucc]2.0.co;2.

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17

Zverkov, N. G. "Late Cretaceous polycotylid plesiosaurs of European Russia." Priroda, no. 8 (1308) (2024): 27. https://doi.org/10.7868/s0032874x24100037.

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Polycotylids are Cretaceous plesiosaurs with a relatively short neck and an elongated snout. For a long time, they were studied mainly based on the fossils from North America. Numerous finds of polycotylids from Russia shed light on their diversity in Late Cretaceous epicontinental seas of Europe. Russian finds demonstrate that some representatives of the family were widely distributed geographically and also shed light on unexpected features of the paleoecology of late representatives of the family.

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18

Bardet, Nathalie, Xabier Pereda Suberbiola, and Nour-Eddine Jalil. "A new polycotylid plesiosaur from the Late Cretaceous (Turonian) of Morocco." Comptes Rendus Palevol 2, no. 5 (2003): 307–15. http://dx.doi.org/10.1016/s1631-0683(03)00063-0.

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19

SATO, TAMAKI, and GLENN W. STORRS. "AN EARLY POLYCOTYLID PLESIOSAUR (REPTILIA: SAUROPTERYGIA) FROM THE CRETACEOUS OF HOKKAIDO, JAPAN." Journal of Paleontology 74, no. 5 (2000): 907–14. http://dx.doi.org/10.1666/0022-3360(2000)074<0907:aepprs>2.0.co;2.

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20

Nicholls, Elizabeth L., and Dirk Meckert. "Marine reptiles from the Nanaimo Group (Upper Cretaceous) of Vancouver Island." Canadian Journal of Earth Sciences 39, no. 11 (2002): 1591–603. http://dx.doi.org/10.1139/e02-075.

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A new fauna of fossil marine reptiles is described from the Late Cretaceous Nanaimo Group of Vancouver Island. The fossils are from the Haslam and Pender formations (upper Santonian) near Courtenay, British Columbia, and include elasmosaurid plesiosaurs, turtles, and mosasaurs. This is only the second fauna of Late Cretaceous marine reptiles known from the Pacific Coast, the other being from the Moreno Formation of California (Maastrichtian). The new Nanaimo Group fossils are some 15 million years older than those from the Moreno Formation. However, like the California fauna, there are no polycotylid plesiosaurs, and one of the mosasaurs is a new genus. This reinforces the provinciality of the Pacific faunas and their isolation from contemporaneous faunas in the Western Interior Seaway.

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21

Bell, Phil R., Federico Fanti, Mark T. Mitchell, and Philip J. Currie. "Marine reptiles (Plesiosauria and Mosasauridae) from the Puskwaskau Formation (Santonian–Campanian), west-central Alberta." Journal of Paleontology 88, no. 1 (2014): 187–94. http://dx.doi.org/10.1666/13-043.

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Plesiosaurs and mosasaurs are identified from the Puskwaskau Formation of west-central Alberta, Canada. These deposits record the final stages during which the Western Interior Seaway remained open to the Boreal Sea to the North and therefore are important for determining the ranges of high-latitude marine reptiles. Polycotylid and elasmosaurid plesiosaurs shared these waters with russellosaurine (including plioplatecarpine) mosasaurs suggesting a diverse ecology of large-bodied marine predators occupied these high-latitude waters in the early Campanian. This locality, situated at 65°N paleolatitude, helps link the poorly known faunas from northern Canada with the better-known faunas from central and southern North America. Rare articulated material from the Puskwaskau Formation urges further investigation of this poorly explored unit.

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22

Palumbo, Ezequiel, and Julia Inés Diaz. "New species and new record of the genus Cheloniodiplostomum (Trematoda, Proterodiplostomidae, Polycotylinae), parasites of freshwater turtles from Argentina." Parasitology Research 117, no. 3 (2018): 767–73. http://dx.doi.org/10.1007/s00436-018-5750-9.

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23

Sato, Tamaki, Xiao-Chun Wu, Alex Tirabasso, and Paul Bloskie. "Braincase of a polycotylid plesiosaur (Reptilia: Sauropterygia) from the Upper Cretaceous of Manitoba, Canada." Journal of Vertebrate Paleontology 31, no. 2 (2011): 313–29. http://dx.doi.org/10.1080/02724634.2011.550358.

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24

SACHS, SVEN, MARKUS WILMSEN, JOSCHUA KNÜPPE, JAHN J. HORNUNG, and BENJAMIN P. KEAR. "Cenomanian–Turonian marine amniote remains from the Saxonian Cretaceous Basin of Germany." Geological Magazine 154, no. 2 (2016): 237–46. http://dx.doi.org/10.1017/s0016756815001004.

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AbstractThe Saxonian Cretaceous Basin constitutes an important source of rare Late Cretaceous marine amniote fossils from Germany. It is also historically famous, having been documented in a series of monographic works published by the distinguished German palaeontologist Hanns Bruno Geinitz in the nineteenth century. The most productive rock units include the upper Cenomanian Dölzschen Formation and upper Turonian Strehlen and Weinböhla limestones (lower Strehlen Formation). A survey of curated specimens recovered from these deposits has now identified isolated teeth of probable polycotylid and elasmosaurid plesiosaurians, as well as several humeri that are referred to protostegid marine turtles. The Saxonian Cretaceous Basin formed a continuous epeiric seaway with the Bohemian Cretaceous Basin during late Cenomanian – Turonian time. A western connection to the North Sea Basin also existed via the North German and Münsterland Cretaceous basins. The Mesozoic marine amniote remains from these regions therefore record a coeval northern European fauna that was probably homogeneous across the northern peri-Tethyan margin during Late Cretaceous time.

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25

SATO, TAMAKI. "A NEW POLYCOTYLID PLESIOSAUR (REPTILIA: SAUROPTERYGIA) FROM THE UPPER CRETACEOUS BEARPAW FORMATION IN SASKATCHEWAN, CANADA." Journal of Paleontology 79, no. 5 (2005): 969–80. http://dx.doi.org/10.1666/0022-3360(2005)079[0969:anpprs]2.0.co;2.

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KEAR, BENJAMIN P., BORIS EKRT, JOSEF PROKOP, and GEORGIOS L. GEORGALIS. "Turonian marine amniotes from the Bohemian Cretaceous Basin, Czech Republic." Geological Magazine 151, no. 1 (2013): 183–98. http://dx.doi.org/10.1017/s0016756813000502.

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AbstractDespite being known for over 155 years, the Late Cretaceous marine amniotes of the Bohemian Cretaceous Basin in the Czech Republic have received little recent attention. These fossils are however significant because they record a diverse range of taxa from an incompletely known geological interval: the Turonian. The presently identifiable remains include isolated bones and teeth, together with a few disarticulated skeletons. The most productive stratigraphical unit is the Lower–Middle Turonian Bílá Hora Formation, which has yielded small dermochelyoid sea turtles, a possible polycotylid plesiosaur and elements compatible with the giant predatory pliosauromorphPolyptychodon. A huge protostegid, together with an enigmatic cheloniid-like turtle,Polyptychodon-like dentigerous components, an elasmosaurid and a tethysaurine mosasauroid have also been found in strata corresponding to the Middle–Upper Turonian Jizera Formation and Upper Turonian – Coniacian Teplice Formation. The compositional character of the Bohemian Cretaceous Basin fauna is compatible with coeval assemblages from elsewhere along the peri-Tethyan shelf of Europe, and incorporates the globally terminal Middle–Upper Turonian occurrence of pliosauromorph megacarnivores, which were seemingly replaced by mosasauroids later in the Cretaceous.

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27

Sato, Tamaki, Tomoya Hanai, Shoji Hayashi, and Tomohiro Nishimura. "A Turonian Polycotylid Plesiosaur (Reptilia: Sauropterygia) from Obira Town, Hokkaido, and Its Biostratigraphic and Paleoecological Significance." Paleontological Research 22, no. 3 (2018): 265–78. http://dx.doi.org/10.2517/2017pr024.

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28

Schmeisser, R. L., and D. D. Gillette. "Unusual occurrence of gastroliths in a polycotylid plesiosaur from the Upper Cretaceous Tropic Shale, southern Utah." PALAIOS 24, no. 7 (2009): 453–59. http://dx.doi.org/10.2110/palo.2008.p08-085r.

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29

O'Keefe, F. Robin. "On the cranial anatomy of the polycotylid plesiosaurs, including new material ofPolycotylus latipinnis, Cope, from Alabama." Journal of Vertebrate Paleontology 24, no. 2 (2004): 326–40. http://dx.doi.org/10.1671/1944.

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30

Frey, Eberhard, Eric W. A. Mulder, Wolfgang Stinnesbeck, Héctor E. Rivera-Sylva, José Manuel Padilla-Gutiérrez, and Arturo Homero González-González. "A new polycotylid plesiosaur with extensive soft tissue preservation from the early Late Cretaceous of northeast Mexico." Boletín de la Sociedad Geológica Mexicana 69, no. 1 (2017): 87–134. http://dx.doi.org/10.18268/bsgm2017v69n1a5.

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31

O'Keefe, F. Robin. "Cranial anatomy and taxonomy ofDolichorhynchops bonnerinew combination, a polycotylid (Sauropterygia: Plesiosauria) from the Pierre Shale of Wyoming and South Dakota." Journal of Vertebrate Paleontology 28, no. 3 (2008): 664–76. http://dx.doi.org/10.1671/0272-4634(2008)28[664:caatod]2.0.co;2.

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32

Schmeisser McKean, Rebecca. "A new species of polycotylid plesiosaur (Reptilia: Sauropterygia) from the Lower Turonian of Utah: Extending the stratigraphic range of Dolichorhynchops." Cretaceous Research 34 (April 2012): 184–99. http://dx.doi.org/10.1016/j.cretres.2011.10.017.

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O’GORMAN, José Patricio, and Rodrigo A. OTERO. "Revision of the short-necked Cretaceous plesiosaurians from New Zealand." Comptes Rendus Palevol, no. 6 (March 14, 2023). http://dx.doi.org/10.5852/cr-palevol2023v22a6.

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Polycotylidae Cope, 1869 is a clade of short-necked plesiosaurians that achieved a cosmopolitan distribution by the Late Cretaceous. Here, the material previously referred to Polycotylidae/Pliosauridae from the Upper Cretaceous of New Zealand is reviewed, concluding that only 2.4% and 7.7% respectively of the total plesiosaurians specimens recovered in these formations (late Campanian-early Maastrichtian Tahora Formation and Campanian-Maastrichtian Conway Formation) belong to Polycotylidae. This proportion is similar to that recorded in upper Campanian-Maastrichtian levels of the Allen, Los Alamitos and La Colonia formations, northern Patagonia (Argentina) and southernmost Chile, but contrasts with the coeval absence of polycotylids in Campanian-Santonian levels of Antarctica and central Chile. These new results improve our knowledge about the representation of Weddellian polycotylids and underline the relative scarcity of Campanian-Maastrichtian records in the Weddellia Province.

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O’Gorman, José P. "Polycotylidae (Sauropterygia, Plesiosauria) from the La Colonia Formation, Patagonia, Argentina: phylogenetic affinities of Sulcusuchus erraini and the Late Cretaceous circum-pacific polycotylid diversity." Cretaceous Research, August 2022, 105339. http://dx.doi.org/10.1016/j.cretres.2022.105339.

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O’Keefe, F. R., P. M. Sander, T. Wintrich, and S. Werning. "Ontogeny of Polycotylid Long Bone Microanatomy and Histology." Integrative Organismal Biology 1, no. 1 (2019). http://dx.doi.org/10.1093/iob/oby007.

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Abstract Plesiosauria is an extinct clade of diapsid marine reptiles that evolved in the Late Triassic and radiated globally for the remainder of the Mesozoic. The recent description of a pregnant specimen of Polycotylus latipinnis demonstrates that some plesiosaurs were viviparous. To establish a baseline of histological data on plesiosaur ontogeny, we sampled the mother and fetus of the gravid plesiosaur specimen. To widen the base of data concerning ontogeny and life history of plesiosaurs, we gathered additional morphologic and histologic data from a securely identified growth series of polycotylids from the Pierre Shale of South Dakota. Paleohistological thin sections were prepared from the three humeri. Both adults show a dense, heavily remodeled cortex consisting entirely of longitudinally oriented secondary osteons, except for a thin rind of superficial primary bone. The mother exhibits an external fundamental system, indicating it was fully mature; the other adult does not. In both adults the cortex grades into a spongy medulla, comprising large vascular canals and erosion rooms surrounded by secondary lamellar trabecular bone, and lacking a marrow cavity. The fetal humerus possesses a medullary region similar to that of the Dolichorhynchops bonneri adult, although its lamellar bone is primary and deposited around calcified cartilage. The medulla is demarcated from the cortex by a prominent Kastschenko’s line. The cortex of the fetus is a relatively thin layer of periosteal woven bone, longitudinally to radially vascularized, and interfingered with columns of osteoblasts surrounded by rapidly-deposited extracellular matrix. The neonate humerus resembles the fetus, with its trabeculae identical in both size and histology, although it lacks calcified cartilage. The cortex is also similar but much thicker, consisting entirely of rapidly deposited, radially vascularized, woven to fibrolamellar bone. The cortex carries a line near its surface. This feature is not a line of arrested growth, but a sudden change in vascular angle and increase in bone density. We argue this feature is a birth line indicating a change in growth regime, possibly in response to increased hydrodynamic forces after birth. The birth line indicates that the neonate was about 40% of maternal length when born. Our histological data demonstrate that polycotylids had very high fetal growth rates, and that birth size was large. Comparison with the geologically oldest plesiosaur confirms that rapid growth evolved in the Triassic, although histological details differ, and the degree to which the polycotylid ontogenetic pattern is generalizable to other plesiosaurs is currently unknown. Further histological research utilizing full growth series is needed, particularly for Jurassic taxa.

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Zverkov, Nikolay G., and Igor A. Meleshin. "Enigmatic large-toothed Campanian polycotylid plesiosaurs with specific dietary preferences and potentially wide distribution." Journal of Palaeogeography, April 2025. https://doi.org/10.1016/j.jop.2024.11.007.

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Persons, Walter Scott, Hallie P. Street, and Amanda Kelley. "A long-snouted and long-necked polycotylid plesiosaur from the Late Cretaceous of North America." iScience, September 2022, 105033. http://dx.doi.org/10.1016/j.isci.2022.105033.

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Clark, Robert O., F. Robin O’Keefe, and Sara E. Slack. "A new genus of small polycotylid plesiosaur from the Upper Cretaceous of the Western Interior Seaway and a clarification of the genus Dolichorhynchops." Cretaceous Research, December 2023, 105812. http://dx.doi.org/10.1016/j.cretres.2023.105812.

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Zverkov, Nikolay G., Dmitry V. Grigoriev, and Anatoly V. Nikiforov. "New polycotylid plesiosaur skeletons from the Upper Cretaceous of the Southern Urals provide additional diagnostic features of Polycotylus sopozkoi and demonstrate its variation." Historical Biology, March 12, 2025, 1–34. https://doi.org/10.1080/08912963.2025.2472161.

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