scholarly journals Ten more years of discovery: revisiting the quality of the sauropodomorph dinosaur fossil record

Palaeontology ◽  
2020 ◽  
Vol 63 (6) ◽  
pp. 951-978
Author(s):  
Daniel D. Cashmore ◽  
Philip D. Mannion ◽  
Paul Upchurch ◽  
Richard J. Butler
2020 ◽  
Author(s):  
Austin J.W. Hendy ◽  
◽  
Shawn Wiedrick
Keyword(s):  

Author(s):  
Thomas A. Hegna ◽  
Javier Luque ◽  
Joanna M. Wolfe

Fossils are critically important for evolutionary studies as they provide the link between geological ages and the phylogeny of life. The Pancrustacea are an incredibly diverse clade, representing over 800,000 described extant species, encompassing a variety of familiar and unfamiliar forms, such as ostracods, tongue worms, crabs, lobsters, shrimps, copepods, barnacles, branchiopods, remipedes, and insects. Having colonized nearly every environment on Earth, from hydrothermal vents to terrestrial habitats, they have a diverse fossil record dating back to the Cambrian (540–485 Ma). The quality of the fossil record of each clade is variable and related to their lifestyle (e.g., free-living versus parasitic, benthic versus pelagic) and the degree of mineralization of their cuticle. We review the systematics, morphology, preservation, and paleoecology of pancrustacean fossils; each major clade is discussed in turn, and, where possible, fossil systematics are compared with more recent data from molecular phylogenetics. We show that the three epic clades of the Pancrustacea—Allotriocarida, Multicrustacea, and Oligostraca—all have Cambrian roots, but the diversification of those clades did not take place until the Middle and Late Paleozoic. We also address the potential affinities of three “problematic” clades: euthycarcinoids, thylacocephalans, and cyclids. We conclude by assessing the future of pancrustacean paleobiology, discussing new morphological imaging techniques and further integration with growing molecular phylogenetic data.


Palaios ◽  
2006 ◽  
Vol 21 (1) ◽  
pp. 86-105 ◽  
Author(s):  
J. S. CRAMPTON ◽  
M. FOOTE ◽  
A. G. BEU ◽  
R. A. COOPER ◽  
I. MATCHAM ◽  
...  

2018 ◽  
Vol 115 (19) ◽  
pp. 4891-4896 ◽  
Author(s):  
Simon J. Maxwell ◽  
Philip J. Hopley ◽  
Paul Upchurch ◽  
Christophe Soligo

The role of climate change in the origin and diversification of early hominins is hotly debated. Most accounts of early hominin evolution link observed fluctuations in species diversity to directional shifts in climate or periods of intense climatic instability. None of these hypotheses, however, have tested whether observed diversity patterns are distorted by variation in the quality of the hominin fossil record. Here, we present a detailed examination of early hominin diversity dynamics, including both taxic and phylogenetically corrected diversity estimates. Unlike past studies, we compare these estimates to sampling metrics for rock availability (hominin-, primate-, and mammal-bearing formations) and collection effort, to assess the geological and anthropogenic controls on the sampling of the early hominin fossil record. Taxic diversity, primate-bearing formations, and collection effort show strong positive correlations, demonstrating that observed patterns of early hominin taxic diversity can be explained by temporal heterogeneity in fossil sampling rather than genuine evolutionary processes. Peak taxic diversity at 1.9 million years ago (Ma) is a sampling artifact, reflecting merely maximal rock availability and collection effort. In contrast, phylogenetic diversity estimates imply peak diversity at 2.4 Ma and show little relation to sampling metrics. We find that apparent relationships between early hominin diversity and indicators of climatic instability are, in fact, driven largely by variation in suitable rock exposure and collection effort. Our results suggest that significant improvements in the quality of the fossil record are required before the role of climate in hominin evolution can be reliably determined.


2021 ◽  
Vol 15 (2) ◽  
pp. 153
Author(s):  
Marcello Guimarães Simões ◽  
Antonio Carlos Marques ◽  
Luiz Henrique Cruz de Mello ◽  
Renato Pirani Ghilardi

The Megadesmidae (Bivalvia, Anomalodesmata) fossil record was examined in order to assess the role of taphonomy in cladistic analysis. Megadesmids are thick-shelled, infaunal, suspension-feeding bivalves. Our data indicate that their fossil record seems biased in favor of thick-shelled, shallow-burrowing genera and/or deep­burrowing forms. Consequently, there is a relation between the mode of life (shallow versus deep) and the resolution and quality of the fossil record. Deep-burrowers (Vacunella) are often preserved in life position offering a more accurate (temporal and spatial) fossil record, adequate for paleoecological inferences, while shallow-burrower shells (Plesiocyprinella), that are more prone to post-mortem transport and temporal mixing, offer a record with poor spatial and temporal resolution. The identification of homoplasy among infauna! bivalves constitutes a major challenge for their cladistic analysis. Within Megadesmidae intrinsic (bauplan limitations) and extrinsic (better preservational potential) factors favor the occurrence and preservation of homoplasy among the deep-burrowers. The implications are: a) clustering of deep-burrowing bivalves (Vacunella, Roxoa) due to parallel homoplasies, forming "adaptive", not necessarily "evolutive" taxa, and b) lower consistency indices in their cladistic analysis. 


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