Pseudosuchia is a group of archosaurian reptiles, defined as all species more closely related to crocodylians than to birds. Living representatives of Pseudosuchia are all members of Crocodylia, a group of semi-aquatic ambush predators found predominantly in freshwater habitats of the tropics. Whereas crocodylians number fewer than 30 species, more than 700 species of pseudosuchians are known from their 250-million-year fossil record. In new research, scientists from the University of York and elsewhere mapped the family tree of Pseudosuchia. They then compared this with data from the fossil record to understand why crocodylians have so few living species.
“Crocodiles and birds share their heritage with dinosaurs, and together with pterosaurs they form a group known as archosaurs or ‘ruling reptiles,’ who date back to the Early Triassic epoch,” said University of York researcher Katie Davis and colleagues.
“Pseudosuchia is a group of archosaurian reptiles, defined as all species more closely related to crocodiles than to birds.”
For their study, the authors built a large phylogeny, which is like a family tree, for all crocodylians and their extinct relatives, allowing them to map out how many new species were being formed and how many species were going extinct.
They then combined this with data about past climate change, in particular temperature and sea level, to assess whether the emergence and extinction of species was linked to climate change.
The researchers also explored whether interactions between species, for example competition, might have played a role, so they calculated estimates of numbers of species at any point in time and compared these against new species and extinctions, using a type of mathematics called information theory.
This allowed the researchers to produce an estimate of whether climate change and species interactions had a direct impact on whether new species were emerging or going extinct.
They found that climate…
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