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Measured sections, Cedar Mountain Formation, Emery County, Utah, showing stratigraphic positions of several key fossil localities and dated ash samples (Cifelli, Kirkland, and others, 1997) in the area of Mussentuchit Wash. See figure 1 for approximate geographic positions of sites and measured sections, and the appendix for descriptions of the sections.
Contexts in source publication
Context 2
... fauna reported herein was recovered as a result of a large-scale collecting program by the OMNH and includes most of the fossils collected between 1990 and 1996, although processing of some material remains incomplete at this writing. Also included are mammalian fossils obtained by one of us (JGE) while at UCM, and non-multituberculate mammal specimens collected under the direction of Michael Nelson while at FHSM. Virtual- ly all mapped outcrops of the Cedar Mountain Formation in the State of Utah were prospected during the course of these investigations. Repeated attempts to find signifi- cant accumulations of microvertebrates in the lower and middle part of the unit were continually frustrated, whereas the upper part of the "shale" member was re- peatedly found to be productive, particularly in Emery County. Here the outcrop of the Cedar Mountain Forma- tion, like that of other Mesozoic units that are exposed in the area, follows the flanks of the main structural feature of the county, the San Rafael Swell (figure 1). Collect- ing was conducted at 31 sites, including two worked by previous investigators; most sites are near the headwaters of Mussentuchit Wash, for which the local fauna reported herein is named ( figure 1). Collecting involved quarry- ing for macrovertebrates and a combination of quarrying and underwater screenwashing, with associated concen- tration and recovery techniques, for microvertebrates ( Cifelli and others, 1996;Madsen, 1996). Articulated remains of macrovertebrates are rare in the upper part of the Cedar Mountain Formation. Accumulations of large bone generally include representation of several taxa, with occasional association of elements belonging to sin- gle individuals. In general, the bone is highly friable; original condition varies from pristine to highly water worn. Microvertebrate specimens are similarly variable in preservation; at the most productive site, OMNH V695, abundant dissociated teeth occur together with dentulous jaws and, rarely, skulls and articulated postcra- nia. Most of the microvertebrate and macrovertebrate localities appear to represent lag concentration of both channel-and floodplain-derived materials, left in over- bank deposits, although oxbow and other paleoenviron- (after Nelson and Crooks, 1987) and approximate positions of OMNH fossil localities in the upper part of the "shale" member. Sites shown in inset, lower left, are in the immediate vicinity of Mussentuchit Wash; tight clustering of sites 19-27, 29, and 31 precludes separate plotting of each at this scale. Bold-faced letters A-C refer to positions of measured sections shown in figure 2 and described in the appendix. OMNH site numbers (see figure 2 for stratigraphic placement of representative sites): 1, V213; 2, V214; 3, V234, 4, V235; 5, V236; 6, V237; 7, V238; 8, V239;9, V240;10, V694;11, V695;12, V696;13, V794;14, V795;15, V796;16, V801 (=FHSM locality RRQ or Rough Road Quarry;see Nelson and Crooks, 1987;Eaton and Nelson, 1991);17, V820 (=REQ or Robison's Eggshell Quarry;see Nelson and Crooks, 1987;Eaton and Nelson, 1991;Fiorillo, this volume);18, V823 (=MNA locality 1072;see Eaton and Nelson, 1991);19, V824;20, V825;21, V826;22, V827;23, V828;24, V847;25, V864;26, V865;27, V866;28, V867;29, V868;30, V869;31, V870. ments are also ...
Context 3
... fauna reported herein was recovered as a result of a large-scale collecting program by the OMNH and includes most of the fossils collected between 1990 and 1996, although processing of some material remains incomplete at this writing. Also included are mammalian fossils obtained by one of us (JGE) while at UCM, and non-multituberculate mammal specimens collected under the direction of Michael Nelson while at FHSM. Virtual- ly all mapped outcrops of the Cedar Mountain Formation in the State of Utah were prospected during the course of these investigations. Repeated attempts to find signifi- cant accumulations of microvertebrates in the lower and middle part of the unit were continually frustrated, whereas the upper part of the "shale" member was re- peatedly found to be productive, particularly in Emery County. Here the outcrop of the Cedar Mountain Forma- tion, like that of other Mesozoic units that are exposed in the area, follows the flanks of the main structural feature of the county, the San Rafael Swell (figure 1). Collect- ing was conducted at 31 sites, including two worked by previous investigators; most sites are near the headwaters of Mussentuchit Wash, for which the local fauna reported herein is named ( figure 1). Collecting involved quarry- ing for macrovertebrates and a combination of quarrying and underwater screenwashing, with associated concen- tration and recovery techniques, for microvertebrates ( Cifelli and others, 1996;Madsen, 1996). Articulated remains of macrovertebrates are rare in the upper part of the Cedar Mountain Formation. Accumulations of large bone generally include representation of several taxa, with occasional association of elements belonging to sin- gle individuals. In general, the bone is highly friable; original condition varies from pristine to highly water worn. Microvertebrate specimens are similarly variable in preservation; at the most productive site, OMNH V695, abundant dissociated teeth occur together with dentulous jaws and, rarely, skulls and articulated postcra- nia. Most of the microvertebrate and macrovertebrate localities appear to represent lag concentration of both channel-and floodplain-derived materials, left in over- bank deposits, although oxbow and other paleoenviron- (after Nelson and Crooks, 1987) and approximate positions of OMNH fossil localities in the upper part of the "shale" member. Sites shown in inset, lower left, are in the immediate vicinity of Mussentuchit Wash; tight clustering of sites 19-27, 29, and 31 precludes separate plotting of each at this scale. Bold-faced letters A-C refer to positions of measured sections shown in figure 2 and described in the appendix. OMNH site numbers (see figure 2 for stratigraphic placement of representative sites): 1, V213; 2, V214; 3, V234, 4, V235; 5, V236; 6, V237; 7, V238; 8, V239;9, V240;10, V694;11, V695;12, V696;13, V794;14, V795;15, V796;16, V801 (=FHSM locality RRQ or Rough Road Quarry;see Nelson and Crooks, 1987;Eaton and Nelson, 1991);17, V820 (=REQ or Robison's Eggshell Quarry;see Nelson and Crooks, 1987;Eaton and Nelson, 1991;Fiorillo, this volume);18, V823 (=MNA locality 1072;see Eaton and Nelson, 1991);19, V824;20, V825;21, V826;22, V827;23, V828;24, V847;25, V864;26, V865;27, V866;28, V867;29, V868;30, V869;31, V870. ments are also ...
Context 4
... of albanerpetontids, a group of superficially salamander-like, Middle Jurassic to Miocene probable lissamphibians (Fox and Naylor, 1982;McGowan and Evans, 1995) are readily identified by their highly pleu- rodont, nonpedicellate, chisel-like, and faintly tricuspid teeth. Dentaries and premaxillae have been collected from various sites in the Cedar Mountain Formation, with several of the former bones preserving the inter- locking symphysial prongs that are unique for albaner- petontids. Although most of the jaws are too fragmen- tary to be identified below the familial level, the best preserved specimens indicate that two albanerpetontid taxa are present. The first of these is represented by three tiny, isolated premaxillae (OMNH 27375, 27979, and 27980), which in their preserved morphologies and small size compare favorably with the holotype (Estes, 1969b, figure 2C-E) and referred premaxillae of Albaner- peton arthridion, a species otherwise known from the early to mid-Albian Antlers Formation of Texas (Fox and Naylor, 1982) and Oklahoma (Cifelli, Gardner, ...
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We report here new evidence of tridactyl dinosaur footprints, comprising nine isolated footprints from a new locality in the Atacama Region, northern Chile. The track-bearing levels are located mainly at La Descubridora ravine and one isolated track near the intersection between La Descubridora and Carriza-lillo ravines, approximately 11 km southea...
Citations
... Recalibration of these aforementioned age ranges through the use of the Fish Canyon sanidine standard age, as well as using alternative methods such as UePb (zircon) radiometric dating, has indicated overall that the temporal placement of the CeT boundary is more likely to have occurred closer to 94 Ma (Meyers et al., 2012;Ogg and Hinnov, 2012;Eldrett et al., 2015;Laurin et al., 2019;Jones et al., 2019). Notwithstanding these challenges, radiometric age dates are invaluable for resolving pervasive inconsistencies in correlating and temporally constraining both marine and continental strata within the Western Interior Basin (WIB) (Cifelli et al., 1997(Cifelli et al., , 1999D'Emic et al., 2019;Miall and Catuneanu, 2019;Nesbitt et al., 2019;Zanno et al., 2019). ...
... Locally in Central Utah, historical and recent biostratigraphic frameworks indicated an upper Cenomanian temporal placement, not limited to: 1) the molluscan genera Inoceramas, Euomphaloceras and Mytiloides submytiloides Seitz (1934) (Zelt, 1985;Kirschbaum and Schenk, 2010, Fig. 3;Eaton et al., 1990, Table 1, pp. 42); 2) various palynomorphs (Garrison et al., 2007; and references therein; Barclay et al., 2015); and 3) trackway studies by Kirkland et al. (2016), Joyce et al. (2016) and Lockley et al. (2018). Support for these original age estimates includes age dating of the underlying Mussentuchit Member (Cifelli et al., 1997(Cifelli et al., , 1999Garrison et al., 2007;Tucker et al., 2020). In Tucker et al. (2020), a detrital zircon sample obtained from the Naturita to constrain the underlying Mussentuchit Member established via CA-TIMS analysis that the lowermost Naturita in the Wasatch Plateau is no older than 95.64 ± 0.11 Ma. ...
... The largest individual of the microvertebrate screen-washed material is represented by a tooth that is 10.1 mm long, though most fall within a range of 1-2 mm in crown height. Similar teeth have long been known from the Cloverly Formation (Ostrom, 1970), Trinity Group (Langston, 1974;Cifelli et al., 1997a), Cedar Mountain Formation (Cifelli et al., 1997b(Cifelli et al., , 1999bKirkland et al., 1999;Frederickson et al., 2017), and Arundel Clay (Lull, Clark & Berry, 1911, plate 20, Fig. 7; Frederickson, Lipka & Cifelli, 2018). Larger teeth (not found in screen-washed material), also include several conical to slightly recurved teeth bearing large carinae, with fine striations radiating apically along the crown (Figs. ...
... Deinonychus has also been reported from the upper part of the Cedar Mountain Formation, Utah: cranial and postcranial remains from the Ruby Ranch Member, reportedly in private hands and not yet described; and isolated teeth from the Mussentuchit Member (Carpenter et al., 2002). Detailed study of large samples of isolated teeth at the NCSM (Avrahami et al., 2018) and the OMNH (Cifelli et al., 1999b;Frederickson, Engel & Cifelli, 2018) have failed to positively identify Deinonychus from the Mussentuchit Member of the Cedar Mountain Formation. Although it is not specifically identified as Deinonychus, a single tooth from the Proctor Lake Dinosaur Locality in the Twin Mountains Formation of Texas is attributed to Dromaeosaurinae (in which Deinonychus is sometimes placed). ...
We present a previously discovered but undescribed late Early Cretaceous vertebrate fauna from the Holly Creek Formation of the Trinity Group in Arkansas. The site from the ancient Gulf Coast is dominated by semi-aquatic forms and preserves a diverse aquatic, semi-aquatic, and terrestrial fauna. Fishes include fresh- to brackish-water chondrichthyans and a variety of actinopterygians, including semionotids, an amiid, and a new pycnodontiform, Anomoeodus caddoi sp. nov. Semi-aquatic taxa include lissamphibians, the solemydid turtle Naomichelys , a trionychid turtle, and coelognathosuchian crocodyliforms. Among terrestrial forms are several members of Dinosauria and one or more squamates, one of which, Sciroseps pawhuskai gen. et sp. nov., is described herein. Among Dinosauria, both large and small theropods ( Acrocanthosaurus , Deinonychus , and Richardoestesia ) and titanosauriform sauropods are represented; herein we also report the first occurrence of a nodosaurid ankylosaur from the Trinity Group. The fauna of the Holly Creek Formation is similar to other, widely scattered late Early Cretaceous assemblages across North America and suggests the presence of a low-diversity, broadly distributed continental ecosystem of the Early Cretaceous following the Late Jurassic faunal turnover. This low-diversity ecosystem contrasts sharply with the highly diverse ecosystem which emerged by the Cenomanian. The contrast underpins the importance of vicariance as an evolutionary driver brought on by Sevier tectonics and climatic changes, such as rising sea level and formation of the Western Interior Seaway, impacting the early Late Cretaceous ecosystem.
... They include, but are not limited to studies to Britt et al. (2007Britt et al. ( , 2009, Burton et al. (2006), Chure et al. (2010), Garrison et al. (2007), Greenhalgh and Britt (2007), Hendrix et al. (2015), Ludvigson et al. (2010), Sprinkel et al. (2012). Some of the earliest radiometric dates from the Mussentuchit Member of the Cedar Mountain Formation were published by Cifelli et al. (1997) and Cifelli et al. (1999). Based on recovered sanidine phenocrysts from smectitic ash horizons, the upper portions of the Cedar Mountain Formation were emplaced around 98.39 ± 0.07 Ma ( 40 Ar/ 39 Ar), which was in close agreement with prior studies by Obradovich (1993;98.5 ...
... Based on Rossignol et al. (2019), these data would indicate a reworking or non-contemporaneous pattern of volcanilithic-rich sediment emplacement at the Cifelli #2 fossil quarry, rather than primary emplacement of volcaniclastic ash. Addressing this concern is beyond the scope of this particular study; but in 2019, our team resampled the volcaniclastic/volcanilithic horizons described by Cifelli et al. (1997Cifelli et al. ( ,1999, including V695 and V826, and these are currently being re-assessed. ...
... Bernissartiid teeth have been reported outside Europe from the Albian Trinity Formation, Texas (Langston 1974;Thurmond 1974) and the Albian-Cenomanian Cedar Mountain Formation, Utah (Cifelli et al. 1999). Isolated tribodont teeth have also been attributed to ?Bernissartia from the Middle and Upper Saurian Beds at Tendaguru, Tanzania, which are dated to late Kimmeridgian and post-Tithonian-pre-Valanginian, respectively (Heinrich et al. 2001). ...
Since the description of Isisfordia duncani, a number of new extinct species and revisions of previously described species have prompted a variety of contradicting phylogenetic hypotheses on the topology of Neosuchia. As a consequence, a consensus on the rooting of Eusuchia in relation to other neosuchian clades has not been reached and the origin of the group remains unsettled. Exemplifying this, Bernissartia fagesii, from the Early Cretaceous of Belgium, has long been considered a key taxon for understanding the origin of Eusuchia, but more recent hypotheses found support for a more basal position, as an ally to goniopholidids, paralligatorids or atoposaurids. Because many details of the anatomy of the type specimen are hidden by glue and the sediment adhering to the fossils, a number of characters are pending confirmation. Based on computed tomography data, we extract bones of the cranium and mandibles, describe new characters and re-evaluate anatomical details in the lectotype specimen. Our phylogenetic analysis confirms that B. fagesii is a derived neosuchian, unrelated to atoposaurids, goniopholidids and paralligatorids. We recover B. fagesii and Koumpiodontosuchus aprosdokiti in a basal position within Eusuchia, together with Susisuchidae, a group of gondwanan neosuchians containing Susisuchus and Isisfordia, which here form a polytomy with Hylaeochampsidae. The presence/absence of pterygoid-bound internal choanae cannot be used to fully resolve relationships at the neosuchian–eusuchian transition because of the variability of this character even at the familial level, as recently reported within susisuchids and bernissartiids. There is no doubt that true eusuchians were present in Laurasia as early as the Early Cretaceous, the hylaeochampsid Hylaeochampsa vectiana being the oldest (Barremian) undoubted representative. But whether the Eusuchia were also present in southern landmasses depends on solving the phylogenetic position of susisuchids and other less known gondwanan forms within or outside Eusuchia.
... Pycnodonts were initially considered to be exclusively marine fishes (Agassiz, 1835;Woodward, 1912;Nursall, 1996a), although their remains have since been recorded in non-marine deposits from Tunisia (Cuny et al., 2010), USA (Cifelli et al., 1999), Brazil (Silva Santos, 1970;Wenz, 1989Wenz, , 1991Poyato-Ariza and Wenz, 2002), France (Cavin et al., 2020), Hungary (Szab o et al., 2016), the United Kingdom (Sweetman et al., 2014;Austen et al., 2010), Thailand (Cavin et al., 2009) and now in Morocco (Sereno et al., 1996, and this paper) Fig. 1). ...
... At present, only three unambiguous baenid fossils are known from the Early Cretaceous, in particular the holotype specimens of Arundelemys dardeni Lipka et al., 2006, Trinitichelys hiatti Gaffney, 1972, and Protobaena wyomingensis (Gilmore, 1919) from the Aptian-Albian of Maryland, Texas, and Wyoming, respectively. A broad set of mostly unfigured fragmentary remains from the Early Cretaceous of Nevada (Bonde et al., 2008), Montana (Oreska et al., 2013), Oklahoma (e.g., Cifelli et al., 1997), and Utah (e.g., Cifelli et al., 1999) may represent fossil baenids as well, but are too incomplete to allow rigorous identification. ...
Baenidae is a clade of paracryptodiran turtles known from
the late Early Cretaceous to Eocene of North America. The proposed
sister-group relationship of Baenidae to Pleurosternidae, a group of turtles
known from sediments dated as early as the Late Jurassic, suggests a ghost
lineage that crosses the early Early Cretaceous. We here document a new
species of paracryptodiran turtle, Lakotemys australodakotensis gen. and sp. nov., from the Early
Cretaceous (Berriasian to Valanginian) Lakota Formation of South Dakota
based on a poorly preserved skull and two partial shells. Lakotemys australodakotensis is most readily
distinguished from all other named Late Jurassic to Early Cretaceous
paracryptodires by having a broad, baenid-like skull with expanded
triturating surfaces and a finely textured shell with a large suprapygal I
that laterally contacts peripheral X and XI and an irregularly shaped
vertebral V that does not lap onto neural VIII and that forms two
anterolateral processes that partially separate the vertebral IV from
contacting pleural IV. A phylogenetic analysis suggests that Lakotemys australodakotensis is a baenid,
thereby partially closing the previously noted gap in the fossil record.
... Previous microvertebrate studies of the Mussentuchit Member have documented the remains of more than 90 species (Gardner, 1994(Gardner, , 1996(Gardner, , 1999bCifelli et al., 1997Cifelli et al., , 1999Fiorillo, 1999;Kirkland et al., 1999Kirkland et al., , 2016Nydam, 1999Nydam, , 2000aNydam, , 2000bNydam, , 2002Goldberg, 2000;Nydam & Cifelli, 2002;Cifelli, 2004;Garrison et al., 2007;McDonald et al., 2017), illuminating one of the most diverse Mesozoic assemblages in North America sampled to date. These taxa were discovered through extensive screen-washing and microvertebrate sampling during the latter part of the 20th century by the Oklahoma Museum of Natural History (Cifelli, 1996;Cifelli, Madsen & Larson, 1996;Cifelli et al., 1997Cifelli et al., , 1999 with a smaller effort aimed at studying the microvertebrates from a single dinosaur locality by the College of Eastern Utah (Garrison et al., 2007). ...
... Previous microvertebrate studies of the Mussentuchit Member have documented the remains of more than 90 species (Gardner, 1994(Gardner, , 1996(Gardner, , 1999bCifelli et al., 1997Cifelli et al., , 1999Fiorillo, 1999;Kirkland et al., 1999Kirkland et al., , 2016Nydam, 1999Nydam, , 2000aNydam, , 2000bNydam, , 2002Goldberg, 2000;Nydam & Cifelli, 2002;Cifelli, 2004;Garrison et al., 2007;McDonald et al., 2017), illuminating one of the most diverse Mesozoic assemblages in North America sampled to date. These taxa were discovered through extensive screen-washing and microvertebrate sampling during the latter part of the 20th century by the Oklahoma Museum of Natural History (Cifelli, 1996;Cifelli, Madsen & Larson, 1996;Cifelli et al., 1997Cifelli et al., , 1999 with a smaller effort aimed at studying the microvertebrates from a single dinosaur locality by the College of Eastern Utah (Garrison et al., 2007). Microvertebrate data collection continues through ongoing research by the North Carolina Museum of Natural Sciences and the Field Museum of Natural History. ...
... 2) indicate that the stratigraphically highest OMNH sites occur at about 13 and 17 meters below the contact with the Naturita Formation (named the Dakota Formation in the aforementioned reference). Site OMNH V824 may occur closer to the Naturita Fm.; however, Cifelli et al. (1999) state that the contact is covered in the field area of their localities so its exact distance below the contact is uncertain. The COI locality is therefore located considerably higher in section than OMNH sites previously reported, raising the likelihood of greater influence from the transgressing WIS. ...
The vertebrate fauna of the Late Cretaceous Mussentuchit Member of the Cedar Mountain Formation has been studied for nearly three decades, yet the fossil-rich unit continues to produce new information about life in western North America approximately 97 million years ago. Here we report on the composition of the Cliffs of Insanity (COI) microvertebrate locality, a newly sampled site containing perhaps one of the densest concentrations of microvertebrate fossils yet discovered in the Mussentuchit Member. The COI locality preserves osteichthyan, lissamphibian, testudinatan, mesoeucrocodylian, dinosaurian, metatherian, and trace fossil remains and is among the most taxonomically rich microvertebrate localities in the Mussentuchit Member. To better refine taxonomic identifications of isolated theropod dinosaur teeth, we used quantitative analyses of taxonomically comprehensive databases of theropod tooth measurements, adding new data on theropod tooth morphodiversity in this poorly understood interval. We further provide the first descriptions of tyrannosauroid premaxillary teeth and document the earliest North American record of adocid remains, extending the appearance of this ancestrally Asian clade by 5 million years in western North America and supporting studies of pre-Cenomaninan Laurasian faunal exchange across Beringia. The overabundance of mesoeucrocodylian remains at the COI locality produces a comparatively low measure of relative biodiversity when compared to other microvertebrate sites in the Mussentuchit Member using both raw and subsampling methods. Much more microvertebrate research is necessary to understand the roles of changing ecology and taphonomy that may be linked to transgression of the Western Interior Seaway or microhabitat variation.
... In contrast to Brusatte et al. (2015), who found no evidence for a progressive Campanian-Maastrichtian decline in North American theropod faunas using similar SQS analyses (implemented in R; see (Tennant et al. 2016a;Tennant et al. 2016b) and (Alroy 2010c;Alroy 2010a) for comparative discussions), we find a very slight decline that remains constant through publication history, that likely relates to our usage of a slightly different subsampling approach. Aptian subsampled diversity is relatively high due to the more heavily sampled localities from Montana to Texas (Kirkland et al. 1997;Cifelli et al. 1999;Kirkland & Madsen 2007). ...
Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abundance curve, which are largely dependent on databases compiled from the primary published literature. However, how these 'corrected' diversity patterns are influenced by the history of publication remains largely unknown. Here, we investigate the influence of publication history between 1991 and 2015 on our understanding of dinosaur evolution using raw diversity estimates and Shareholder Quorum Subsampling for the three major subgroups: Ornithischia, Sauropodomorpha and Theropoda. We find that, while sampling generally improves through time, there remain periods and regions in dinosaur evolutionary history where diversity estimates are highly volatile (e.g., the latest Jurassic of Europe, the mid-Cretaceous of North America, and the Late Cretaceous of South America). Our results show that historical changes in database compilation can often substantially influence our interpretations of dinosaur diversity. 'Global' estimates of diversity based on the fossil record are often also based on incomplete, and distinct regional signals, each subject to their own sampling history Changes in the record of taxon abundance distribution, either through discovery of new taxa or addition of existing taxa to improve sampling evenness, are important in improving the reliability of our interpretations of dinosaur diversity. Furthermore, the number of occurrences and newly identified dinosaurs is still rapidly increasing through time, suggesting that it is entirely possible for much of what we know about dinosaurs at the present to change within the next 20 years.
... In contrast to Brusatte et al. (2015), who found no evidence for a progressive Campanian-Maastrichtian decline in North American theropod faunas using similar SQS analyses (implemented in R; see ( Tennant, Mannion & Upchurch, 2016a, 2016b) and ( Alroy, 2010aAlroy, , 2010c for comparative discussions), we find a very slight decline that remains constant through publication history, that likely relates to our usage of a slightly different subsampling approach. Aptian subsampled diversity is relatively high due to the more heavily sampled localities from Montana to Texas ( Kirkland et al., 1997;Cifelli et al., 1999;Kirkland & Madsen, 2007). In Africa, there is a Cenomanian radiation ( Fig. 9C) mainly due to the multitaxic theropod dominated Kem Kem beds and other Albian-Cenomanian ('middle' Cretaceous) equivalents in Northern Africa, but this signal might have been altered by time averaging effects constraining a more temporally diluted diversity in a single unit ( Mannion & Barrett, 2013;Evers et al., 2015;Chiarenza & Cau, 2016). ...
Assessments of dinosaur macroevolution at any given time can be biased by the historical publication record. Recent studies have analysed patterns in dinosaur diversity that are based on secular variations in the numbers of published taxa. Many of these have employed a range of approaches that account for changes in the shape of the taxonomic abundance curve, which are largely dependent on databases compiled from the primary published literature. However, how these 'corrected' diversity patterns are influenced by the history of publication remains largely unknown. Here, we investigate the influence of publication history between 1991 and 2015 on our understanding of dinosaur evolution using raw diversity estimates and shareholder quorum subsampling for the three major subgroups: Ornithischia, Sauropodomorpha, and Theropoda. We find that, while sampling generally improves through time, there remain periods and regions in dinosaur evolutionary history where diversity estimates are highly volatile (e.g. the latest Jurassic of Europe, the mid-Cretaceous of North America, and the Late Cretaceous of South America). Our results show that historical changes in database compilation can often substantially influence our interpretations of dinosaur diversity. 'Global' estimates of diversity based on the fossil record are often also based on incomplete, and distinct regional signals, each subject to their own sampling history. Changes in the record of taxon abundance distribution, either through discovery of new taxa or addition of existing taxa to improve sampling evenness, are important in improving the reliability of our interpretations of dinosaur diversity. Furthermore, the number of occurrences and newly identified dinosaurs is still rapidly increasing through time, suggesting that it is entirely possible for much of what we know about dinosaurs at the present to change within the next 20 years. Subjects Evolutionary Studies, Paleontology
... Another piece of evidence that supports the radiation hypothesis to North America from Asia is the appearance of several major dinosaurian clades with Asian ancestry in the Early Cretaceous terrestrial deposits of western North America (Zanno and Makovicky, 2011). These clades include ankylosaurids, ceratopsians, dromaeosaurids, hadrosaurids, ornithomimids, oviraptorids, pachycephalosaurids, and tyrannosaurids (e.g., Ostrom, 1970;Cifelli et al., 1999;Gangloff, 1998;Makovicky and Sues, 1998;Garrison et al., 2007;McDonald et al., 2010;Zanno and Makovicky, 2011). ...
... In western North America the remains of basal tyrannosaurids are known from isolated teeth and have been identified from several pre-Campanian localities such as the upper Little Sheep Mudstone Member of the Cloverly Formation (Aptian-Albian) of Wyoming (Zanno and Makovicky, 2011), the Wayan Formation (Albian-Cenomanian) of Idaho (Krumenacker et al., 2016), Mussentuchit Member of the Cedar Mountain Formation (Cenomanian) (Kirkland et al., 1997Cifelli et al., 1999), Dakota Formation (Cenomanian) and Straight Cliffs Formation (Turonian-early Campanian) Parrish, 1999) of Utah, and the Milk River Formation (Santonian) of Alberta (Larson, 2008). Tyrannosaurids were also identified in younger deposits of the Claggett Formation (early middle Campanian) of Montana-Wyoming . ...
We report on tyrannosaurid skeletal fossil remains from the early Campanian deposits of the Allison Member of the Menefee Formation in New Mexico. The skeletal fossil remains described here, which were found at several localities in the Menefee Formation include the left postorbital, isolated lateral tooth, thoracic rib shaft, anterior right scapula, and partial right metatarsal II. Overall morphology of the isolated skeletal remains resembles that of albertosaurine tyrannosaurids from younger Upper Cretaceous deposits of Alberta and Montana. At present the taxonomic identity of the Menefee tyrannosaurid cannot be ascertained because other skeletal elements are unknown, including the diagnostic cranial bones. Among the bones described here the postorbital exhibits a distinct morphology. The lateral surface of the postorbital has a prominent rugosity that extends along the anterolateral margin of the ventral postorbital ramus. The rugosity forms a characteristic sinuous flange-like structure, which then slightly extends into-and covers a small portion of the orbit and is best seen in lateral and anterior views. The flange-like structure is angled at 30° angle with respect to the ventral ramus. The characteristic position of the flange-like structure results in the formation of an elongated shallow fossa. However, the relatively small size the bones suggests that they belong to juvenile animals. The presence of tyrannosaurids in the Menefee Formation marks one the earliest occurrences of these iconic theropods in southwestern part of North America and adds to the previous assumption of the origin of Tyrannosauridae in this continent.
