Table 1. List of squamate taxa currently known from Chadronian and Orellan strata in North America (compiled from Estes 1983; Sullivan and Holman 1996; this study). An asterisk indicates that the taxon is known exclusively from the Medicine Pole Hills l.f.; a dagger indicates an uncertain record. Listing of taxa in the same row is not meant to imply direct descendance, only that they cannot be excluded from the same lineage. Species-level taxon names are given where available; in cases where specimens from the Medicine Pole Hills l.f. cannot adequately be diagnosed to species level, but also cannot be excluded from a species already known from the Chadronian, only the previously known species is listed, with the conservative assumption that the specimen(s) in question do represent that species.

Chadronian	Orellan
Tinosaurus sp.*
Polychrus charisticus sp. nov.*
Iguanid MPH-1*
Iguanid MPH-2*
Tuberculacerta pearsoni gen. et sp. nov.*	Paraphrynosoma greeni
cf. Aciprion sp.*	Aciprion formosum
Iguanid MPH-3*
Iguanid MPH-4*
Cypressaurus hypsodontus
"Crotaphytus" oligocoenicus
Scincoid MPH-1*	Scincid, new taxon
"Palaeoxantusia" borealis
cf. Rhineura sp.	Rhineura hatcheri
Spathorhynchus natronicus
Hyporhina tertia	Hyporhina antiqua
	Exostinus serratus
Anguimorph MPH-1*	Parophisaurus pawneensis
Diploglossine MPH-1*
cf. Peltosaurus sp.	Peltosaurus granulosus
Helodermoides sp. nov.?*	Helodermoides sp.
Helodermoides tuberculatus
Xenosaurid MPH-1*
	Lowesaurus matthewi
Saniwa edura sp. nov.*
	Coprophis dakotaensis
Boavus sp.	Boavus cf. occidentalis
Calamagras weigeli	Calamagras angulatus
	Calamagras murivorus
	Helagras orellanensis
Ogmophis compactus	Ogmophis compactus†
	Geringophis vetus
	Texasophis galbreathi