A field guide to mesozoic birds and other winged dinosaurs

newly found and externally visible differences in coloration or feathering.
This scenario shows some of the inherent problems with creating a
field guide to extinct animals. However, while informed by an abundance
of speculation, such guides can be useful in illustrating our general view of
the known diversity of extinct animals while pointing out plausibly identifiable
distinguishing features. In some cases, I have deliberately over-generalized
known traits from a few species to entire groups. For example, some
troodontids (Anchiornis huxleyi, Jinfengopteryx elegans) preserve fronds of
tail feathers which cover nearly the entire skeletal tail down to the base.
While we can’t be sure this pattern held true for all troodontids, and while
it’s extremely likely that exceptions existed, I have restored most troodontids
with extensive tail fronds. Similarly, most other known ornithodesmid
and basal avialan fossils have short fronds restricted to the tail tip; again, I
carried this over to all eudromaeosaurians as a unifying trait to aid identification.
Some features, like the distribution and types of feathers, beaks,
teeth, and even coloration, can be more confidently inferred based on evolutionary
relationships and ecology: this process is explained in the sections
below.
Above: Troodon formosus (top) and Saurornitholestes explanatus (bottom) restored to the
same length with identical feathering and coloration.
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