A citation, although they’re easy to find:

“Under the original ESA, a species was defined to
include ‘‘any subspecies of fish or wildlife or plants
and any other group of fish or wildlife of the same
species or smaller taxa in common spatial arrangement that interbreed when mature’’ (ESA, Section
3(15)). In 1978, the Act was amended to eliminate
this language and replace it with the current DPS
concept. The new definition provides that a species
includes ‘‘any subspecies of fish or wildlife or plants,
and any distinct population segment of any species
of vertebrate fish or wildlife which interbreeds when
mature’’ (ESA, Section 4)”

http://www.bearbiology.com/fileadmin/tpl/Downloads/URSUS/Vol_18/U18_1_Rosen.pdf

The Terrestrial Vertebrates category is divided in two: Amphibians and Reptilomorpha, which is surely a category you can describe as “reptiles” in the broad sense.

Reptilomorpha divides in several extinct groups and then Amniota.

Amniota divides between Synapsida (mammals and extinct “reptile-like” relatives) and Reptilia (reptiles in the narrow sense, including birds and dinosaurs).

Reptilia divides in Anapsida (leading to Testudina: turtles) and Romerida (leading to Diapsida, which includes all other reptiles and, of course, birds and dinosaurs).

It is not that Reptilia or Reptilomorpha are not monophyletic, it is just that traditionally we decided that a widespread subclade was out of the group (birds and mammals respectively).

Similarly brown bears are monophyletic in the graphic above, if anything it is polar bears, a subclade of brown bears it seems, which are not.

Woot!!!

Polar Bears and the Irish share a common ancestor

Wikipedia sites recent paper in PNAS that says: “the specimen was estimated to be 130–110 ky old, which is significantly older than any other known polar bear subfossils”. The paper itself suggest the split at around 150 kya.