Lecture on Epicyon and the Evolution of Canids

Introduction

• Epicyon: One of the largest dogs ever, as big as a brown bear.
• Active during the Miocene epoch (16M-7M years ago).
• Part of the Borophaginae subfamily, also known as "bone-crushing dogs".
• Existed for over 30 million years in North America.

Canidae Family Overview

• Family includes dogs, wolves, foxes (34 species today).
• Potential origin: Prohesperocyon (around 36 million years ago in southern Texas) though its classification as a canid is debated.
• Shared traits: Meat-eating habits, auditory bullae (protect middle ear bones, enhance low-frequency hearing).

Subfamilies of Canids

1. Hesperocyoninae

   • Adapted to Late Eocene.
   • Main genus: Hesperocyon (~37 million years ago).
   • Characteristics: retractable claws, small nimble bodies, possible tree climbers.
   • Transition to Oligocene: Shift to hunting larger herbivores in grasslands.

2. Borophaginae (Bone-Crushing Dogs)

   • Evolution from Archaeocyon (~30 million years ago).
   • Characteristics: Shorter jaws, thicker premolars.
   • Mid-Miocene: Transition to larger, carnivorous species like Epicyon.
   • Epicyon haydeni: Largest canid, massive cheek teeth for bone crushing.
   • Hunting strategies: Likely pounce-pursuit predators, potentially hunted in packs.
   • Decline due to competition from canines and cats.

3. Caninae (Surviving Subfamily)

   • First appearance: Over 30 million years ago.
   • One of the earliest: Leptocyon (early Oligocene).
   • Evolution: Long legs for distance running, reduction of "big toe".
   • Hunting method shifted to endurance running (e.g., wolves today).
   • Survival advantage: Adaptation to long-distance running, competition with new predators like cats.
   • Spread to South America, Eurasia, Africa, and Australia.

Competition and Extinction

• Competition with cats like Pseudaelurus (ambush predators).
• Cats’ retractable claws provided hunting advantages.
• Last bone-crushing dogs (genus Borophagus) extinct ~2 million years ago.
• Hesperocyonines extinct ~13 million years ago.
• Caninae's adaptability ensured their survival and spread.

Cautionary Tale

• Dominant predators often face precarious positions when environments change.
• Adaptability is key to survival.

Conclusion and Thanks

• Special thanks to Wix for supporting PBS Digital Studios.
• Encouragement to visit Wix.com for website building tools.
• Gratitude to supporters and viewers, and call to subscribe and join Patreon for rewards.