7 results found
Chiarenza A, Mannion P, Lunt D, et al., 2019, Ecological niche modelling does not support climatically-driven dinosaur diversity decline before the Cretaceous/Paleogene mass extinction, Nature Communications, Vol: 10, ISSN: 2041-1723
In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise. The latest Cretaceous (Campanian–Maastrichtian [83–66 Ma]) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised.
Mannion P, Chiarenza A, Godoy P, et al., 2019, Spatiotemporal sampling patterns in the 230 million year fossil record of terrestrial crocodylomorphs and their impact on diversity, Palaeontology, ISSN: 0031-0239
The 24 extant crocodylian species are the remnants of a once much more diverse and widespread clade. Crocodylomorpha has an approximately 230 million year evolutionary history, punctuated by a series of radiations and extinctions. However, the group's fossil record is biased. Previous studies have reconstructed temporal patterns in subsampled crocodylomorph palaeobiodiversity, but have not explicitly examined variation in spatial sampling, nor the quality of this record. We compiled a dataset of all taxonomically diagnosable non‐marine crocodylomorph species (393). Based on the number of phylogenetic characters that can be scored for all published fossils of each species, we calculated a completeness value for each taxon. Mean average species completeness (56%) is largely consistent within subgroups and for different body size classes, suggesting no significant biases across the crocodylomorph tree. In general, average completeness values are highest in the Mesozoic, with an overall trend of decreasing completeness through time. Many extant taxa are identified in the fossil record from very incomplete remains, but this might be because their provenance closely matches the species’ present‐day distribution, rather than through autapomorphies. Our understanding of nearly all crocodylomorph macroevolutionary ‘events’ is essentially driven by regional patterns, with no global sampling signal. Palaeotropical sampling is especially poor for most of the group's history. Spatiotemporal sampling bias impedes our understanding of several Mesozoic radiations, whereas molecular divergence times for Crocodylia are generally in close agreement with the fossil record. However, the latter might merely be fortuitous, i.e. divergences happened to occur during our ephemeral spatiotemporal sampling windows.
Tennant J, Chiarenza AA, Baron M, 2018, How has our knowledge of dinosaur diversity through geologic time changed through research history?, PeerJ, Vol: 6, ISSN: 2167-8359
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.
Chiarenza AA, Cau A, 2016, A large abelisaurid (Dinosauria, Theropoda) from Morocco and comments on the Cenomanian theropods from North Africa, PeerJ, Vol: 4, ISSN: 2167-8359
We describe the partially preserved femur of a large-bodied theropod dinosaur fromthe Cenomanian “Kem Kem Compound Assemblage” (KKCA) of Morocco. Thefossil is housed in the Museo Geologico e Paleontologico “Gaetano GiorgioGemmellaro” in Palermo (Italy). The specimen is compared with the theropod fossilrecord from the KKCA and coeval assemblages from North Africa. The combinationof a distally reclined head, a not prominent trochanteric shelf, distally placed lessertrochanter of stout, alariform shape, a stocky shaft with the fourth trochanter placedproximally, and rugose muscular insertion areas in the specimen distinguishes itfrom Carcharodontosaurus, Deltadromeus and Spinosaurus and supports referral toan abelisaurid. The estimated body size for the individual from which this femur wasderived is comparable to Carnotaurus and Ekrixinatosaurus (up to 9 meters in lengthand 2 tons in body mass). This find confirms that abelisaurids had reached theirlargest body size in the “middle Cretaceous,” and that large abelisaurids coexistedwith other giant theropods in Africa. We review the taxonomic status of thetheropods from the Cenomanian of North Africa, and provisionally restrict theLinnean binomina Carcharodontosaurus iguidensis and Spinosaurus aegyptiacus tothe type specimens. Based on comparisons among the theropod records from theAptian-Cenomanian of South America and Africa, a partial explanation for theso-called “Stromer’s riddle” (namely, the coexistence of many large predatorydinosaurs in the “middle Cretaceous” record from North Africa) is offered in termof taphonomic artifacts among lineage records that were ecologically andenvironmentally non-overlapping. Although morphofunctional and stratigraphicevidence supports an ecological segregation between spinosaurids and the otherlineages, the co-occurrence of abelisaurids and carcharodontosaurids, two groupsshowing several craniodental convergences tha
Chiarenza AA, Foffa D, Young MT, et al., 2015, The youngest record of metriorhynchid crocodylomorphs, with implications for the extinction of Thalattosuchia, CRETACEOUS RESEARCH, Vol: 56, Pages: 608-616, ISSN: 0195-6671
Dal Sasso C, Insacco G, Chiarenza AA, et al., 2014, FIRST RECORD OF ICHTHYOSAURS IN SICILY (UPPER TRIASSIC OF MONTE SCALPELLO, CATANIA PROVINCE), RIVISTA ITALIANA DI PALEONTOLOGIA E STRATIGRAFIA, Vol: 120, Pages: 71-82, ISSN: 0035-6883
Chiarenza AA, Dalla Vecchia FM, Rosso A, et al., 2013, The Early Jurassic ichthyosaur Stenopterygius in the collections of the Museo di Scienze della Terra, Universita di Catania (Italy), BOLLETTINO DELLA SOCIETA PALEONTOLOGICA ITALIANA, Vol: 52, Pages: 19-25, ISSN: 0375-7633
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