Long before computers,
paleontologists used their wits and lists of traits to tie taxa together in evolutionary sequences. Some nestings and match-ups were easy. Others were… not so easy.
Watson 1957 (Fig. 1) produced his version of the reptile family tree produced without the benefit of computers and matrices. In those days, if relationships were unknown they were unlinked in the graphics. Rarely is the entire gamut of the Reptilia presented, so here we have an early version of the large reptile tree.
Some changes since 1957
In the large reptile captorhinids, caseids, pterosaurs, Milleretta and Saurosternon moves to the new Lepidosauromorpha. Hovasaurus, Tangasaurus and thalattosaurs move to the new Archosauromorpha. These changes are noted by the overlying colors. Still, all in all, not too far off the mark!!!
Some things did not change since 1957
Tanytrachelos, Tanystropheus and Macrocnemus nested in Watson’s tree (Fig.1) at the base of the lepidosaurs distinct from the protorosaurs. That shows some insight. Turtles also nested with the lepidosaurs. Protorosaurs and younginids nest in Watson’s tree at the base of the “Thecodontia” now considered the Archosauriformes, as they do in the large reptile tree. Watson assumed these groups all descended from the Millerosauria. The large reptile tree confirms this relationship, with the exception of the lepidosauromorph, Milleretta, which does not nest with the protodiapsid archosauromorphs Milleropsis and Millerosaurus, but is closer to caseids and turtles and lots of other rarely reported taxa.
From then til now
Nowadays we know the origin of reptiles goes back a little further than the Late Carboniferous. Furthermore, we can connect all the leaves on the reptile family tree without the missing links and with complete resolution.
Earlier a similar chronology of fossil reptiles using a computer-generated phylogram mated to a time chart was presented. It gives a fuller picture of Watson’s tree.
Missed this earlier milestone a few days ago: We’ve passed 800 posts here.
Watson DMS 1957. On Millerosaurus and the Early History of the Sauropsid Reptiles. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 240: 673: 325-400.