Final answer:
The remaining reptile group when excluding birds is termed d) Sauropsida, which encompasses nonavian reptiles such as crocodiles, lizards, snakes, and turtles while recognizing the phylogenetic connection of birds to the Archosauria clade.
Step-by-step explanation:
If birds are excluded from the reptile clade for practical reasons, the remaining reptile group is termed Sauropsida. The clade Sauropsida includes the class Reptilia with four living clades of nonavian organisms: Crocodilia (crocodiles and alligators), Sphenodontia (tuataras), Squamata (lizards and snakes), and Testudines (turtles). When we refer to birds in a context separate from reptiles for convenience or practical reasons, we should understand that this division is not phylogenetically accurate since birds are indeed part of the Archosauria clade along with crocodilians and extinct dinosaurs, and have evolved from theropod dinosaurs within this broader group.