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Abstract

Sauropod dinosaurs have a temporally disjunct distribution in the North AmericanWestern Interior during Cretaceous time, here referred to as the sauropod hiatus. Sauropod body and ichnofossils are present in inland basinal and coastal deposits of Aptian-Albian age in Wyoming, Texas, Oklahoma, and Arkansas. Body fossils of sauropods (the titanosaurid Alamosaurus) occur in inland basinal deposits of Maastrichtian age in Texas, New Mexico, Utah, and Wyoming. No sauropods of Cenomanian-Campanian age are known from a Western Interior sedimentary record dominated by coastal deposits and essentially devoid of inland basinal deposits. Dinosaur ichnofaunas from late Albian coastal deposits in New Mexico, Oklahoma, and Colorado lack sauropod footprints, and thus suggest sauropod disappearance from Western Interior coastal environments by the end of Early Cretaceous time.These observations suggest two scenarios: (1) sauropods abandoned Western Interior coastal environments at the end of the Albian, but persisted in Western Interior inland basinal environments throughout Cretaceous time, or (2) sauropods became extinct in the Western Interior at the end of the Albian and reinvaded during the Maastrichtian. Choosing between these scenarios depends on an evaluation of negative evidence. However, the close phylogenetic relationship of Alamosaurus to South American titanosaurids, the absence of sauropod fossils in inland deposits of the Campanian Two Medicine and Judith River Formations, and the availability of a dispersal route between North and South America near the end of Cretaceous time support the second scenario. Thus, sauropods apparently became extinct in the Western Interior near the end of the Albian, then reinvaded from South America during the Maastrichtian but were only able to establish themselves in inland basinal environments. The extinction of sauropods in the Western Interior at the end of Early Cretaceous time may reflect an unrecognized terrestrial extinction coincident with the well-known severe marine extinction caused by a major late Albian regression.

New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

“…Of note is that the contemporaneous OTU comprising a somphospondylan from the Cloverly Formation (‘Cloverly titanosauriform’) is recovered as the sister taxon to Sauroposeidon in our EIW9 analysis (figure 5 c ), which would support the referral of this material to that taxon by D'Emic & Foreman [102]. Stratigraphically younger sauropods are unknown from North America until the Maastrichtian, with the appearance of Alamosaurus sanjuanensis ([65,103]; though see Ryan & Evans [104] for a possible Santonian sauropod occurrence from Canada), although whether this ‘sauropod hiatus’ reflects an extinction followed by ‘re-invasion’, a sampling bias or some combination of both, remains uncertain [9,105].…”

“…Alamosaurus is known from the Maastrichtian of the USA [14,64], and is currently the only recognized titanosaur from North America [65,121]. Its biogeographic origin has long been the subject of debate [9,74,103,105,122], with alternative phylogenetic hypotheses supporting dispersal from either: (i) South America, based on a sister taxon relationship with latest Cretaceous taxa such as Baurutitan britoi or Saltasaurus loricatus (e.g. [1,38,40]); or (ii) East Asia, based on a sister taxon relationship with Opisthocoelicaudia skarzynskii (e.g.…”

“…Titanosaurs were a diverse and globally distributed group of Cretaceous sauropod dinosaurs [1-3] that included the largest terrestrial animals ever known [4,5]. For much of the history of their study, titanosaurs were thought to have been a primarily Gondwanan radiation of sauropods [6][7][8][9], known mainly from the Late Cretaceous [10], with only a small number of taxa recognized from Laurasia [11][12][13][14]. In recent decades, the discovery of new titanosaurs from the latest Cretaceous of Eurasia (e.g.…”

High-precision40Ar/39Ar geochronology and the advent of North America’s Late Cretaceous terrestrial fauna

“…The fauna also includes 33 (46%) stratigraphic range extensions for North American taxa and 28 (39%) on a global scale. Most notable among last North American occurrences is that of Sauropoda, the large, perhaps high-browsing, herbivores that dominated faunas of the Late Jurassic (6) and reappeared briefly in the latest Cretaceous through immigration (19). The vertebrate fauna of the uppermost Cedar Mountain Formation greatly resembles later Cretaceous assemblages, sharing 80% of taxa (at lowest identifiable level); by contrast, only 60% of Cedar Mountain taxa appear in earlier faunas.…”

A Sauropod Tooth from the Santonian of Hungary and the European Late Cretaceous ‘Sauropod Hiatus’

“…Similarly to the ‘sauropod hiatus’ hypothesis proposed by Lucas and Hunt 51 to account for the absence of sauropod fossils for the largest part of the mid to Late Cretaceous interval in North America, Le Loeuff  8 and Le Loeuff and Buffetaut 15 suggested that the fossil record supports the absence of sauropods from the Cenomanian to late Campanian continental vertebrate record of Europe. This assertion was based on the fact that until the end of the 1990’s not even a single bone or footprint, certainly referable to this group, was known from the, admittedly few, European vertebrate localities representing this time period.…”