Question

give two similarities between each of the skull that might lead to the conclusion that these are all related species

Answer 1

I don’t have the skulls or images you’re referring to — could you upload them or say which specimens they are? With that I can point out specific shared features.

Meanwhile, here are two strong, general types of similarities that, if present in each skull, would support the conclusion that they are related species — and why those features matter:

1. Dental pattern and tooth morphology
- What to look for: same dental formula (number of incisors, canines, premolars, molars), similar tooth shape and cusp patterns (e.g., bunodont vs. selenodont), consistent size relationships among tooth types.
- Why it matters: teeth reflect ancestry and diet-related developmental patterns. Complex similarities in cusp arrangement and tooth counts are unlikely to be identical by chance and often indicate common descent.

2. Cranial architecture (braincase shape, position of the foramen magnum, zygomatic arches, orbital position)
- What to look for: comparable neurocranium size/shape, same relative position of the foramen magnum (indicates head posture/locomotion), similar zygomatic arch shape/robustness, similar orbital orientation and spacing.
- Why it matters: these features are developmentally integrated and reflect underlying skull growth patterns inherited from a common ancestor. Multiple shared cranial characters together strengthen the inference of relatedness.

A couple of quick caveats: convergent evolution can produce similar-looking features in unrelated lineages (especially gross functional traits like heavy crests or enlarged orbits), so stronger evidence comes from multiple independent, detailed characters (especially dental and sutural/osteological details) and ideally from other data (postcranial anatomy, genetics).

If you upload the skull photos or list the taxa, I’ll give two specific similarities for each skull pair.