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Paleogeographic map of the Western Interior seaway (©2014 Ron Blakey, Colorado Plateau Geosystems, Inc.).
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North-south provinciality among Campanian and/or Maastrichtian vertebrates, especially dinosaurs,
in the Western Interior basin of North America (specifically, between West Texas and southern Alberta, Canada) has been accepted by many vertebrate paleontologists for about 30 years. However, a critical review indicates that the case for provinciality...
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Context 1
... Late Cretaceous time, a seaway extended from the Gulf of Mexico to the Arctic Ocean across a broad swath of western North America, dividing it into western and eastern land areas (Fig. 1). To the west of the Western Interior seaway, a tectonically and volcanically active land called Laramidia (Archibald, 1996) sourced rivers that flowed eastward to the seaway's western shoreline. The sediments deposited by these rivers, and on their floodplains and deltas, and the sediments deposited in the Western Interior seaway, are ...
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... and/or Maastrichtian thus rests on dinosaur distribution, as advocates of that provinciality have long made clear. The strata that yield the Campanian-Maastrichtian dinosaur fossils extend from Alaska to Mexico, though analysis of biogeographic patterns has only focused on the area from southern Alberta to either New Mexico or West Texas (Fig. 1). In this region, numerous dinosaur genera and species represent 13 family-level clades of ornithischians and saurischians. The Campanian ornithischian dinosaurs belong to the following families: Ankylosauridae, Ceratopsidae, Hadrosauridae, Pachycephalosauridae, and Thescelosauridae. The saurischian theropods include the following ...
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... a very precise point can be made about the correlation of the chasmosaurines named from Utah and Alberta by . The type material of Kosmoceratops richardsoni and Utahceratops gettyi from Utah are from the lower middle unit and upper lower unit of the Kaiparwoits Formation, very close to 76 Ma based on the isotopic ages (Roberts et al., 2013, fig. 6.3). The holotype of Vagaceratops irvinensis, in contrast, is near the very top of the Dinosaur Park Formation, very close to a radioisotopic age of 75 Ma. Thus, Vagaceratops is not contemporaneous with Kosmoceratops and Utahceratops, and all are older than Pentaceratops from New Mexico, despite the statements to the contrary by . Sullivan ...
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A single block containing five articulated osteoglossomorphs was recovered from the Paskapoo Formation of southern Alberta, during development of a residential community in Calgary. Two of the specimens represent a new species of Joffrichthys, and the other three represent a new genus and species of osteoglossomorph. The discovery of a new species...
Citations
... A final comment in relation to Estelestes ensis and (the rest of?) the Glasbiidae is related to the apparent paradox that this taxon, despite being younger in time, is clearly more generalized than Glasbius from the Late Cretaceous of the same North American continent. Probably, the lower latitude of Lomas las Tetas de Cabra with respect to the localities bearing Glasbius remains has played a role among other paleoenvironmental and biogeographical factors (but see Lucas et al., 2016). Humid tropical areas tend to function both as "cradles" (areas of radiation of taxa) and as "museums" (areas of persistence of generalized taxa). ...
Estelestes ensis Novaceck et al., 1991 is a curious Paleogene metatherian mammal recognized on the basis of a single specimen from Baja California (Mexico) in southern North America. It comes from early Eocene (Wasatchian age) levels of the Las Tetas de Cabra Formation at “Marsupial Hill” in the Lomas Las Tetas de Cabra site (also known as Punta Prieta; see Novaceck et al., 1991). The specimen consists of a fragmentary left mandible with the last premolar, the roots of the first two molars, and almost complete last two molars (Fig. 1). It was referred to the Didelphini (Marsupialia, Didelphimorphia, Didelphidae, Didelphinae) even though Novaceck et al. (1991) stated that the overall morphology of the type specimen poses intriguing problems regarding its relationships. For example, the very deep, robust jaw of Estelestes distinguishes it from any other Holarctic “didelphine” (at the time Novaceck et al., 1991 published their work, both the concept and extent of Didelphidae and Didelphinae were much broader than today). Interestingly, they concluded that Estelestes had close affinities with “ Mirandotherium ” (lapsus calami for Mirandatherium ), from the early Eocene of Itaboraí, in southeastern Brazil. “Resemblance between the two taxa is nevertheless striking, once again raising the possibility of close relationships among certain early members of the Northern Hemisphere and South American Didelphinae” (Novaceck et al., 1991, p. 16). The affinities of Mirandatherium are contested, having been regarded as part of the Didelphimorphia (e.g., de Paula Couto, 1952a) or Microbiotheria (e.g., Marshall, 1987; McKenna and Bell, 1997; Oliveira and Goin, 2011), or even as an alphadontian (Carneiro, 2019).
... In fact, it is not only biased towards tyrannosaurids, and, although many other types of dinosaurs had high species diversity in Laramidia during the Campanian period, the fossil record is also mostly biased towards places such as Alberta, Montana, New Mexico, and southern Utah (e.g., Longrich et al. 2013;Thomson et al. 2013;Longrich 2014). Such phenomena suggest that some degree of north-south provinciality was present within Campanian dinosaurs in Laramidia (e.g., Lehman 1987;Sampson et al. 2010;Longrich 2014;Bell et al. 2015;Dalman et al. 2022) but it is still debatable whether there were latitudinal gradients between northern and southern faunas (Longrich 2014;Lucas et al. 2016;Voris et al. 2020). Partly, this is because of the very rare nature of Campanian dinosaur fossils from areas such as Colorado, Wyoming, and central and eastern Utah that represent components of the faunas that were located between northern and southern assemblages of Laramidia (Thomson et al. 2013;Foster and Hunt-Foster 2015). ...
... Of note, Thomson et al. (2013) suggested such a boundary between the northern and southern assemblages may have been at the same latitude with the Williams Fork Formation fauna, based on tyrannosaurid metatarsals from the Nelsen Formation of Utah that were proposed to be similar to those of northern taxa (i.e., Albertosaurinae, Daspletosaurus spp.). Various mecha nisms, such as flora, climate, geographical barriers, and competition with dinosaurs of closely related species, have been identified as factors leading to the provincialism of these Laramidia dinosaurs (e.g., Longrich 2014), but it is still unclear what was the main factor (Lucas et al. 2016). Perhaps it is a combined result of all of these mechanisms, and at least some of the faunas which have been compared to support this hypothesis are slightly different in age, so the difference in the faunas of individual members may actually be due to the difference in age (Lucas et al. 2016;Dalman et al. 2022). ...
... Various mecha nisms, such as flora, climate, geographical barriers, and competition with dinosaurs of closely related species, have been identified as factors leading to the provincialism of these Laramidia dinosaurs (e.g., Longrich 2014), but it is still unclear what was the main factor (Lucas et al. 2016). Perhaps it is a combined result of all of these mechanisms, and at least some of the faunas which have been compared to support this hypothesis are slightly different in age, so the difference in the faunas of individual members may actually be due to the difference in age (Lucas et al. 2016;Dalman et al. 2022). The proposed character evidence (presence or absence of the ridge in the caudal surface of metatarsal IV) was included in the phylogenetic analysis of Loewen et al. (2013), but the utility of this feature was questioned by Brusatte and Carr (2016). ...
A right theropod pedal ungual phalanx II-3 from the Campanian Williams Fork Formation of northwestern Colorado is described, and a combination of features, including the large size, tapering distal tip, robust and stout overall form, triangular cross-section, and a relatively flat ventral surface allows a confident referral to Tyrannosauridae Osborn, 1906. Although this specimen was found in a relatively southern state, the proximal articular surface of this ungual is similar to that of Gorgosaurus libratus Lambe, 1914, a taxon found in the northern state, Alberta. Although based on limited evidence, this may suggest that the range of tyrannosaurids considered endemic to the north of Laramidia extended farther south than previously thought.
... Additionally, the age of the Naashoibito Member of the Ojo Alamo Formation has been debated as to whether it is from the Edmontonian or Lancian (e.g., . Figure pools information from multiple sources, including the Geologic Map of New Mexico (2003), Lucas (2003, 2006), Weil (2008a, 2008b), Lucas et al. (2009Lucas et al. ( , 2016, Sullivan (2011, 2016), Jasinski, Sullivan, and Lucas (2011);Jasinski, Lucas, and Moscato (2011); Koenig et al. (2012), Sullivan and Jasinski (2012), Brusatte (2014, 2016), Jasinski et al. ( , 2020, , and Ksepka et al. (2017). Clarkfork, Clarkforkian; Ed, Edmontonian; Lanc, Lancian; Maast, Maastrichtian; NALMA, North American Land Mammal Age; NALVA, North American Land-Vertebrate Age; Sel, Selandian; Tiff, Tiffanian vertebrae, we utilize proximal (=anterior or cranial) and distal (=posterior or caudal) directions or surfaces. ...
... As suggested by Jasinski et al. (2020), there may still be some vicariance between biogeographical regions. There is a clear connection between many of the dinosaurs (e.g., ankylosaurids, hadrosaurids, pachycephalosaurids, ornithomimids, tyrannosaurids) of Asia and North America during the Late Cretaceous (e.g., Arbour et al., 2014;Brusatte and Carr, 2016;Dalman et al., 2017;Lucas et al., 2016;McFeeters et al., 2017;Prieto-M arquez, 2010;Sullivan, 1999 and how these came about, including possibilities for migration patterns, vicariance, and/or convergence, still need to be investigated. ...
... Additionally, some of this variation is particularly hard to definitively identify in the fossil record, especially sexual dimorphism (e.g., Mallon, 2017). Many studies have been conducted on morphological variation, particularly within fossil taxa (e.g., Arbour et al., 2016;Bell, 2011;Burns et al., 2015;Carter et al., 2021;Currie, 2003aCurrie, , 2003bDalman et al., 2017Dalman et al., , 2021Delcourt & Iori, 2018;Dodson, 1976;Evans et al., 2013Evans et al., , 2014Fabrezi et al., 2017;Gee & Jasinski, 2021;Grillo & Delcourt, 2017;Jasinski, 2011Jasinski, , 2013Jasinski, , 2015bJasinski, , 2018Jasinski et al., 2018Jasinski et al., , 2022Jasinski & Moscato, 2014Jasinski & Wallace, 2014Ji et al., 2011;Johnson, 2020;Johnson et al., 2021;Lacovara et al., 2014;Lehman, 1987;2001;Longrich, 2014;Lucas et al., 2011Lucas et al., , 2016Machado et al., 2013;Moscato & Jasinski, 2016;Osborn, 1923;Rivera-Sylva et al., 2012;Rowe, Colbert, & Nations, 1981;Sampson et al., 2010;Sullivan et al., 2013;Sullivan, Jasinski, Guenther, & Lucas, 2011;Sullivan, Lucas, & Jasinski, 2011c, 2011dVamberger et al., 2020;Voris et al., 2019). While the only definitive specimen of Dineobellator notohesperus is the holotype (SMP VP-2430), other specimens from the Naashoibito Member argue for the presence of more than one dromaeosaurid taxon in this stratigraphic unit. ...
Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recovered from the latest Cretaceous of the southwestern United States. Reinterpreted and newly described material include several caudal vertebrae, portions of the right radius and pubis, and an additional ungual, tentatively inferred to be from manual digit III. Unique features, particularly those of the humerus, unguals, and caudal vertebrae, distinguish D. notohesperus from other known dromaeosaurids. This material indicates different physical attributes among dromaeosaurids, such as use of the forearms, strength in the hands and feet, and mobility of the tail. Several bones in the holotype exhibit abnormal growth and are inferred to be pathologic features resulting from an injury or disease. Similar lengths of the humerus imply Dineobellator and Deinonychus were of similar size, at least regarding length and/or height, although the more gracile nature of the humerus implies Dineobellator was a more lightly built predator. A new phylogenetic analysis recovers D. notohesperus as a dromaeosaurid outside other previously known and named clades. Theropod composition of the Naashoibito Member theropod fauna is like those found in the more northern Late Cretaceous North American ecosystems. Differences in tooth morphologies among recovered theropod teeth from the Naashoibito Member also implies D. notohesperus was not the only dromaeosaurid present in its environment.
... Subsequent studies concurred with these findings (Lehman, 1987(Lehman, , 1997Sloan, 1969Sloan, , 1976, and some suggested that the biogeographic distribution of multiple vertebrate species (Gates et al., 2010) and plant groups (Burgener et al., 2021) was more complicated than a simple north-south division. Opposition to the provinciality hypothesis centered on the lack of spatiotemporally contiguous faunal and temporal data (Chiarenza et al., 2019;Dean, Chiarenza, & Maidment, 2020;Lucas, Sullivan, Lichtig, Dalman, & Jasinski, 2016;Maidment, Dean, Mansergh, & Butler, 2021;Sullivan & Lucas, 2006), or on phylogenetic trees of dinosaur clades defying expectations of a simple two-zone distribution system (Berry, 2018;Longrich, 2014). Other studies (Fowler & Fowler, 2020;Gates, Jinnah, Levitt, & Getty, 2014;McDonald, Wolfe, Fowler, & Gates, 2021) present results that support the hypothesis of separate biotas in the Western Interior Basin based on clade-specific phylogenetic trees. ...
... In many clades, however, a reliable phylogeny is not available for fossil taxa, so methods utilizing PA ordination, faunal similarity metrics, or simply visual approximations of species biogeography are used to hypothesize the ecosystem-scale interactions within and between formations. The Western Interior Basin of North America is no exception, with most of the biogeographic research being conducted through these methods (e.g., Burgener et al., 2021;Fowler, 2017;Gates et al., 2010;Lehman, 1997;Lucas et al., 2016;Russell, 1967;Sloan, 1969). Other research has centered on the quality of the dataset itself-that is, the adequacy of the fossil record-for determining the biogeographic distribution of organisms, most of which proposes that the record is simply not good enough (Chiarenza et al., 2019;Dean et al., 2020;Maidment et al., 2021). ...
... Incomplete preservation of biotic data is a perennial problem for paleontological analyses that has led previous studies (e.g., Dean et al., 2020;Lucas et al., 2016;Maidment et al., 2021) to question the very practice of attempting to decipher paleobiogeographic patterns. The model discrimination method presented here accepts the fundamental issues presented in previous studies and provides a means to use the data at hand in order to find out which geographic distribution hypotheses are more likely than others without abandoning the practice all together. ...
The geographic ranges in which species live is a function of many factors underlying ecological and evolutionary contingencies. Observing the geographic range of an individual species provides valuable information about these historical contingencies for a lineage, determining the distribution of many distantly related species in tandem provides information about large‐scale constraints on evolutionary and ecological processes generally. We present a linear regression method that allows for the discrimination of various hypothetical biogeographical models for determining which landscape distributional pattern best matches data from the fossil record. The linear regression models used in the discrimination rely on geodesic distances between sampling sites (typically geologic formations) as the independent variable and three possible dependent variables: Dice/Sorensen similarity; Euclidean distance; and phylogenetic community dissimilarity. Both the similarity and distance measures are useful for full‐community analyses without evolutionary information, whereas the phylogenetic community dissimilarity requires phylogenetic data. Importantly, the discrimination method uses linear regression residual error to provide relative measures of support for each biogeographical model tested, not absolute answers or p‐values. When applied to a recently published dataset of Campanian pollen, we find evidence that supports two plant communities separated by a transitional zone of unknown size. A similar case study of ceratopsid dinosaurs using phylogenetic community dissimilarity provided no evidence of a biogeographical pattern, but this case study suffers from a lack of data to accurately discriminate and/or too much temporal mixing. Future research aiming to reconstruct the distribution of organisms across a landscape has a statistical‐based method for determining what biogeographic distributional model best matches the available data.
... Two factors that support this hypothesis include 1) the presence of competition in other paleogeographic niches throughout the Western Interior Basin, and 2) adaptation to an environment (especially its various diseases), which may have prevented the radiation of some species and lineages (Longrich, 2020 personal communication). However, Lucas et al. (2016) offer a counter to this idea, including highlighting differences in the temporal occurrences of many species used to support this hypothesis. ...
... Rather than having distinct northern and southern dinosaurian faunas that has been discussed by other authors (e.g., Lehman, 1997Lehman, , 2001Sampson et al., 2010), it is more likely that these correspond to distinct communities on smaller regional or basin scales. Lucas et al. (2016) discussed issues with the northern and southern faunal hypothesis and in particular, discussed a lack of geographic barriers between the regions, among other things, that would have made dinosaurs migration more difficult if present. With distinct species often present in close geographic proximity in the Late Cretaceous of North America, we hypothesize that high levels of endemism, particularly present in ceratopsids (especially in chasmosaurines), may instead be due to adaptations, and high levels of vicariance, diversification, and speciation within this group. ...
... Much of the vertebrate fauna making up these formations have been studied and non-dinosaurs include chondrichthyans, osteichthyans, anurans, caudates, turtles, squamates, crocodylians, pterosaurs, and mammals (e.g., Armstrong-Ziegler, 1978, 1980Flynn, 1986;Hunt and Lucas, 1993;Lucas et al., 2006;Jasinski et al., , 2018Sullivan and Fowler, 2011;Sullivan et al., 2011dSullivan et al., , 2013Sullivan and Jasinski, 2012;Sullivan and Lucas, 2015;Jasinski et al., 2018). The strata also preserve a diverse dinosaur fauna, including various theropods, such as caenagnathids, dromaeosaurids, ornithomimids, oviraptorosaurs, troodontids, tyrannosaurids, and avians, and herbivores, such as ankylosaurid and nodosaurid ankylosaurians, chasmosaurine and centrosaurine ceratopsids, lambeosaurine and saurolophine hadrosaurids, pachycephalosaurids, and titanosauriform sauropods (e.g., Gilmore, 1916;Sullivan, 1999;Sullivan et al., 2000Sullivan et al., , 2011aSullivan et al., , 2011cLucas et al., 2009Lucas et al., , 2016Carr and Williamson, 2010;Sullivan and Lucas, 2010, 2014Jasinski et al., , 2020Koenig et al., 2012;Sullivan and Jasinski, 2012;Arbour et al., 2014;Jasinski, 2015;Robinson et al., 2015;Gates et al., 2021). This suggests a thriving dinosaur and vertebrate fauna, particularly one with high-turnover, leading to high biodiversity at the end of the Cretaceous in northwestern New Mexico, part of which included Bisticeratops froeseorum (Fig. 28). ...
A nearly complete skull of a new ceratopsid dinosaur, Bisticeratops froeseorum, is described from the Farmington Member of the Kirtland Formation (late Campanian, Upper Cretaceous) of New Mexico. Bisticeratops is distinguished by several diagnostic cranial characters, including those of the premaxilla (stepped dorsal margin), maxilla (short jugal process lacking the ventral pocket-like fossa), jugal (short maxillary process of the jugal), and palpebral ornamentation (short with moderate ornamentation). It differs from other known chasmosaurines, especially from stratigraphically older species in the same geographic region, Pentaceratops sternbergi and Titanoceratops ouranos, by a strongly reduced jugal process of the maxilla and an unusual maxilla/jugal contact, which forms a shallow, triangular-shaped lateroposteriorly concave sulcus. A phylogenetic analysis recovers Bisticeratops froeseorum as sister species to the unnamed Almond Formation chasmosaurine and as a member of a potentially new southern clade of chasmosaurines, outside the Triceratopsini, and distinct from other southern Laramidian chasmosaurines such as Pentaceratops. The dinosaur fauna of the Farmington Member is comparatively poorly understood, especially compared to stratigraphically older faunas in the San Juan Basin. Therefore, the new, presumably rare species Bisticeratops froeseorum, together with several recently named and described chasmosaurines such as Navajoceratops sullivani, Sierraceratops turneri, and Terminocavus sealeyi, add to the diversity and disparity of chasmosaurines and provides further support for latitudinal variation in the ceratopsid fauna during the Late Cretaceous interval in the Western Interior Basin of North America.
... Other workers have disagreed. For example, Lucas et al. (2016) questioned various aspects of Brinkman et al.'s (2013) interpretations and argued that Brinkman et al. (2013) compared faunas from only two areas (Utah and Alberta), noting that at least three geographic points were necessary to properly evaluate latitudinal patterns. The Lowerverse locality in West Texas (~35 N) now provides a requisite third geographic datum and its osteichthyan fauna adds support to Brinkman et al.'s (2013) assertions regarding a latitudinal segregation of at least some species during the Late Cretaceous. ...
... Why such patterns are observed among various Late Cretaceous terrestrial and aquatic vertebrate communities is not well understood. Whether they are the result of day length, climate variability, eustacy, paleoenvironmental and/or geophysical factors, diachronicity, or sampling bias remain the subjects of ongoing research and debate (e.g., Lehman, 1997Lehman, , 2001Brinkman, 2005;Lehman et al., 2006;Lucas and Sullivan, 2006;Sullivan and Lucas, 2006;Sankey, 2008;Gates et al., 2010Gates et al., , 2012Vavrek and Larsson, 2010;Brinkman et al., 2013;Loewen et al., 2013;Nydam et al., 2013;Lucas et al., 2016;Berry, 2018;Lehman et al., 2019;Burgener et al., 2021;Dalman et al., 2022;Maidment et al., 2021). ...
A new osteichthyan fauna from the lower Campanian Aguja Formation of West Texas represents a critical southern datum regarding the interpretation of faunal differences observed among Upper Cretaceous, non-marine fish assemblages of the Western Interior. Bony fish are represented within the “Lowerverse” local fauna by as many as 21 primitive and advanced species. The Lowerverse locality is situated at the southern end of a geographic range of paracontemporaneous localities in Laramidia that have produced a number of similarly well-sampled osteichthyan assemblages. A comparison of the Lowerverse bony fish fauna with those of southern Utah and southern Alberta supports previous hypotheses regarding the latitudinal segregation of some species in the Western Interior. Given their ubiquity throughout Late Cretaceous North America in both time and space, the north-south geographical segregation of garfishes in the Western Interior is especially revealing in this regard and reveals that some species were markedly provincial during the Campanian. Taxonomic inconsistencies among these regional faunas are observed even at higher taxonomic ranks and infer that such differences are sending meaningful ecological signals.
... However, the current literature contains few well-constrained studies of the interplay between latitudinal and depositional gradients during the Late Cretaceous and how such interactions could have shaped the vertebrate communities of the time. Furthermore, the dynamics and ecological consequences of complex, large-scale Earth system events (e.g., major transgressions and regressions), capable of reshaping the geography and environment of entire depositional basins, have been addressed only at a conceptual level (Weishampel and Horner, 1987;Horner et al., 1992;Upchurch et al., 2002;Brinkman, 2003;Bell and Snively, 2008;Butler and Barrett, 2008;Fanti and Miyashita, 2009;Mannion et al., 2012Mannion et al., , 2014Lucas et al., 2016;Chiarenza et al., 2019). This dearth of information is primarily due to the lack of geographic and temporal continuity among fossil-bearing localities, combined with difficulties in tracing timerepresentative surfaces across multiple terrestrial sedimentary units (Sullivan and Lucas, 2006;Holland and Loughney, 2021). ...
... A neochoristodere possibly referable to Champsosaurus is even known from Turonian-Coniacian deposits on Axel Heiberg Island in the Canadian Arctic, occurring with turtles, amiids, lepisosteids, and teleosts (Tarduno et al., 1998;Friedman et al., 2003;Vandermark et al., 2007). Crocodylians have previously been documented in Campanian strata from Mexico to southern Alberta (Markwick, 1998;Gates et al., 2010;Lucas et al., 2016;Rivera-Sylva et al., 2019), but Amiot et al. (2004) suggested the southern Alberta occurrence was near the northern limit of their range, defined by their inability to tolerate climates in which the mean temperature of the coldest month averaged below 5-10 • C. The presence of a small number of crocodyliform elements at the DC Bonebed alongside a much larger quantity of Champsosaurus material is consistent with the seemingly greater ability of Champsosaurus to thrive in high-latitude environments. However, Champsosaurus is also notably abundant in the vertebrate assemblage from Saskatchewan Landing, in which crocodyliforms do not occur (Gilbert et al., 2018). ...
Patterns of Late Cretaceous terrestrial vertebrate diversity across North America have been interpreted primarily in terms of biogeographic provincialism driven by latitude or coastal-inland habitat gradients. A major difficulty in determining the influence of these two gradients is the existence of some large gaps in the terrestrial fossil record, notably the ‘Bearpaw gap’ caused by a transgression of the inland Bearpaw Seaway during the latter part of the Campanian. In this context, the terrestrial fauna preserved in the Campanian deposits of the Wapiti Formation (west-central Alberta, Canada) is crucial for addressing the information deficit. Deposited at the edge of the palaeo-circumpolar region, Unit 3 of the strictly terrestrial Wapiti Formation (WU3) is coeval with the ‘Bearpaw gap’, a period when the terrestrial record from better-sampled areas elsewhere in Canada and the U.S.A. gives way to marine sediments. Here we show, based largely on evidence from the recently discovered DC (Dinosaur-Chelonian) Bonebed locality, that the diverse WU3 vertebrate fauna shares similarities with lowland to marginal marine ecosystems in the Oldman and Dinosaur Park formations which were deposited in southern Alberta prior to the Bearpaw gap. In addition, a major change in faunal composition demarcates the upper boundary of WU3, related to the disappearance of the Bearpaw Sea in Canada. Data presented here help, first and foremost, to bridge an ~1.2-million-year gap in the North American record of Campanian terrestrial vertebrates. Resemblances between the WU3 vertebrate fauna and slightly older assemblages from southern Alberta underscore the importance of determining the spatiotemporal changes in environmental factors (e.g., coastal proximity). The occurrence of one seemingly endemic lizard, together with differences in relative taxon abundance, suggest additional latitude-correlated factors, implicating both latitudinal and coastal-inland habitat gradients in driving the taxonomic composition of Late Cretaceous terrestrial faunas.
... Lucas et al. (2016: 202) have argued that Pachyrhinosaurinae von Huene, 1950 has priority over Centrosaurinae under the Article 61 of the ICZN (International Commission on Zoological Nomenclature, 1999). However, the name Pachyrhinosaurinae has not been used in the literature recently and even Lucas et al. (2016) used Centrosaurinae for the clade in question. ...
Ornithischians form a large clade of globally distributed Mesozoic dinosaurs, and represent one of their three major radiations. Throughout their evolutionary history, exceeding 134 million years, ornithischians evolved considerable morphological disparity, expressed especially through the cranial and osteodermal features of their most distinguishable representatives. The nearly two-century-long research history on ornithischians has resulted in the recognition of numerous diverse lineages, many of which have been named. Following the formative publications establishing the theoretical foundation of phylogenetic nomenclature throughout the 1980s and 1990s, many of the proposed names of ornithischian clades were provided with phylogenetic definitions. Some of these definitions have proven useful and have not been changed, beyond the way they were formulated, since their introduction. Some names, however, have multiple definitions, making their application ambiguous. Recent implementation of the International Code of Phylogenetic Nomenclature (ICPN, or PhyloCode) offers the opportunity to explore the utility of previously proposed definitions of established taxon names. Since the Articles of the ICPN are not to be applied retroactively, all phylogenetic definitions published prior to its implementation remain informal (and ineffective) in the light of the Code. Here, we revise the nomenclature of ornithischian dinosaur clades; we revisit 76 preexisting ornithischian clade names, review their recent and historical use, and formally establish their phylogenetic definitions. Additionally, we introduce five new clade names: two for robustly supported clades of later-diverging hadrosaurids and ceratopsians, one uniting heterodontosaurids and genasaurs, and two for clades of nodosaurids. Our study marks a key step towards a formal phylogenetic nomenclature of ornithischian dinosaurs.
... We also tested the effect of paleobiogeographic and/or formational boundary faunas, considering that the dinosaur fauna was likely geographically cosmopolitan, at least within Laramidia (Lehman 1987(Lehman , 2001; but see Vavrek and Larsson 2010;Lucas et al. 2016). In a secondary analysis, we assembled a faunal list for the Lance Formation and combined it with that of the Hell Creek Formation. ...
The end-Cretaceous (K/Pg) mass extinction event is the most recent and well-understood of the “big five” and triggered establishment of modern terrestrial ecosystem structure. Despite the depth of research into this event, our knowledge of upper Maastrichtian terrestrial deposits globally relies primarily on assemblage-level data limited to a few well-sampled formations in North America, the Hell Creek and Lance Formations. These assemblages disproportionally affect our interpretations of this important interval. Multiple investigations have quantified diversity patterns within these assemblages, but the potential effect of formation-level size-dependent taphonomic biases and their implications on extinction dynamics remains unexplored. Here, the relationship between taphonomy and body size of the Hell Creek Formation and Lance Formation dinosaurs and mammals are quantitatively analyzed. Small-bodied dinosaur taxa (<70 kg) are consistently less complete, unlikely to be articulated, and delayed in their description relative to their large-bodied counterparts. Family-level abundance (particularly skeletons) is strongly tied to body mass, and the relative abundance of juveniles of large-bodied taxa similarly is underrepresented. Mammals show similar but nonsignificant trends. The results are remarkably similar to those from the Campanian-aged Dinosaur Park Formation, suggesting a widespread strong taphonomic bias against the preservation of small taxa, which will result in their seemingly depauperate diversity within the assemblage. This taphonomically skewed view of diversity and abundance of small-bodied taxa amid our best late Maastrichtian samples has significant implications for understanding speciation and extinction dynamics (e.g., size-dependent extinction selectivity) across the K/Pg boundary.
... He then used species-area relationships to estimate an actual number of dinosaur species in the range of 628 to 1078 were alive toward the end of the Cretaceous and experienced abrupt elimination at the end-Cretaceous extinction. This analysis, however, is assumption laden, particularly regarding the degree of endemism of dinosaur species, a topic of considerable debate (e.g., Lucas et al., 2016). McGhee et al. (2004) identified an end-Cretaceous mass extinction on land as a category I extinction, meaning that existing ecoystems collapsed and were replaced by new ecosystems post extinction. ...
A critical review of putative nonmarine mass extinctions associated with the so-called “Big 5 mass extinctions” of marine invertebrates (Late Ordovician, Late Devonian, end Permian, end Triassic and end Cretaceous) as well as a likely sixth mass extinction in the marine realm, the end-Guadalupian extinction, reveals little evidence of coeval marine and nonmarine mass extinctions. Little lived on land during the Ordovician other than a bryophyte-like flora that appears to have been diversifying, not going extinct, during the Late Ordovician. No case can be made for mass extinctions on land coeval with the marine extinctions of the Late Devonian-land plant diversity increased into the Carboniferous, and the tetrapod fossil record is inadequate to identify any mass extinctions. A case can be made for coeval plant/tetrapod extinctions and the end-Guadalupian marine extinctions, so this may be the first coeval marine-nonmarine mass extinction. However, problems of timing and questions about the extent of the nonmarine late/end-Guadalupian extinctions indicate that further research is needed. There were no mass extinctions of land plants, insects or tetrapods across the Permo–Triassic boundary. The Late Triassic was a time of low origination and high extinction rates on land and in the seas; there was no single end-Triassic mass extinction in either realm. The end-Cretaceous provides the strongest case for coeval
land–sea mass extinctions, but there is no mass extinction of land plants, evidence of insect extinction is based on assumption-laden analyses of proxies for insect diversity and the tetrapod extinction was very selective. So, whether the nonmarine extinction at the end of the Cretaceous was a mass extinction is worth questioning. Part of the inability to identify nonmarine mass extinctions stems from taphonomic megabiases due to the relatively
poor quality and uneven sampling of the nonmarine fossil record. Extinction resistance and resilience of terrestrial organisms is also a likely factor in the dearth of nonmarine mass extinctions, and this merits further investigation.
