基因组学与地球科学迅猛发展,古生物学进入纵深发展新时代——2017年古生物学热点回眸

 古生物学是以化石为主要研究对象,研究地质历史时期的生物界及其发展的科学,属于地球科学与生命科学之间的交叉学科。随着生命科学基因组学与地球系统科学的迅猛发展,古生物学这门古老学科进入了纵深发展的新时代,不断涌现振奋人心的研究进展与新发现。本文回顾了2017年国际古生物研究领域取得的重要进展与研究热点,并介绍了中国古生物学界2017年在早期生命、早期后口动物、古脊椎动物、古人类、古DNA以及演化古生物学等研究方向做出的重要贡献。     

Jurassic radiation of large Branchiopoda (Arthropoda: Crustacea) using secondary structure-based phylogeny and relaxed molecular clocks

The phylogenetic relationships of large Branchiopoda have been one of the most controversial issues in the studies of Crustacea. This study attempts to tackle systematic problems concerning “conchostracan” and anostracan evolution, by analyzing ribosomal RNA sequences of both mitochondrial (12S) and nuclear genes (18S). Phylogenetic trees are reconstructed with these data from 27 genera belonging to 18 families, using maximum parsimony procedures, maximum likelihood, and Bayesian analysis coupled with Markov chain Monte Carlo (MCMC) techniques under mixed and doublet models. The results suggest that Diplostraca (Conchostraca+Cladocera) form a monophyletic group, with Spincaudata and Cladoceromorpha being sister groups and Laevicaudata a basal lineage of Diplostraca; Notostraca and Diplostraca together form the monophyletic Phyllopoda. Within Diplostraca, Conchostraca is paraphyletic in contrast to the traditional systematic classification. Relaxed molecular clock analysis, using multiple fossil calibration points, indicates that the conchostracan three genera—Imnadia, Caenestheriella， and Caenestheria, emerged during Jurassic; most anostracan groups, such as Polyartemiinae, Chirocephalinae, Branchinectidae, and Streptocephalidae, experienced an adaptive radiation during Jurassic, and probably related with the fragmentation of the Pangea supercontinent.     

Did dinosaurs have any relation with dung‐beetles? (The origin of coprophagy)

It is widely accepted that Mesozoic ecosystems were basically similar to Cenozoic ecosystems and it has been proposed that the role of dung‐beetles in those ecosystems was identical to that of today, but the dung of dinosaurs were used as a source of food instead of the dung of mammals. While dinosaurs have been known since Triassic, Scarabeids are present in the fossil records probably since Lower Jurassic. But a very important metabolic feature of dinosaurs has not been taken into account, the connection between digestive and uro‐genital systems. So here we propose the hypothesis that coprophagy in dung‐beetles has been associated, since it began, with mammals.     

Jurassic radiation of large Branchiopoda (Arthropoda: Crustacea) using secondary structure-based phylogeny and relaxed molecular clocks

The phylogenetic relationships of large Branchiopoda have been one of the most controversial issues in the studies of Crustacea. This study attempts to tackle systematic problems concerning “conchostracan” and anostracan evolution, by analyzing ribosomal RNA sequences of both mitochondrial (12S) and nuclear genes (18S). Phylogenetic trees are reconstructed with these data from 27 genera belonging to 18 families, using maximum parsimony procedures, maximum likelihood, and Bayesian analysis coupled with Markov chain Monte Carlo (MCMC) techniques under mixed and doublet models. The results suggest that Diplostraca (Conchostraca+Cladocera) form a monophyletic group, with Spincaudata and Cladoceromorpha being sister groups and Laevicaudata a basal lineage of Diplostraca; Notostraca and Diplostraca together form the monophyletic Phyllopoda. Within Diplostraca, Conchostraca is paraphyletic in contrast to the traditional systematic classification. Relaxed molecular clock analysis, using multiple fossil calibration points, indicates that the conchostracan three genera—Imnadia, Caenestheriella， and Caenestheria, emerged during Jurassic; most anostracan groups, such as Polyartemiinae, Chirocephalinae, Branchinectidae, and Streptocephalidae, experienced an adaptive radiation during Jurassic, and probably related with the fragmentation of the Pangea supercontinent.