Bony labyrinth morphology clarifies the origin and evolution of deer

Area of Science:

• Paleontology
• Evolutionary Biology
• Zoology

Background:

• Deer (Cervidae) originated in the Early Miocene of Eurasia, with their evolutionary relationships still debated despite various analytical approaches.
• The bony labyrinth, a structure within the inner ear, offers potential for resolving phylogenetic questions in deer and other mammal groups.
• Previous studies have yielded some consensus on deer relationships but leave many evolutionary questions unresolved.

Purpose of the Study:

• To investigate the phylogenetic relationships and evolutionary history of deer using the shape of the bony labyrinth.
• To provide new age estimates for key evolutionary divergences within the Cervidae family.
• To distinguish between stem and crown lineages of Cervidae and clarify the monophyly of specific deer subfamilies.

Main Methods:

• Analysis of bony labyrinth shape in 29 species of living and fossil deer using 3D geometric morphometrics.
• Application of cladistics to the morphological data derived from the bony labyrinth shape.
• Comparative analysis of bony labyrinth shape variability between deer subfamilies (Capreolinae and Cervinae).

Main Results:

• The fossil deer Euprox furcatus (13.8 Ma) is unambiguously assigned to crown Cervidae, suggesting crown deer originated at least 4 Ma.
• Capreolinae exhibit greater variability in bony labyrinth shape compared to Cervinae.
• Morphological evidence supports the monophyly of Old World Capreolinae, including Hydropotes (Chinese water deer), and the sister relationship between Megaloceros giganteus and Dama (fallow deer).

Conclusions:

• The bony labyrinth shape is a valuable character for understanding deer phylogeny and evolution.
• This study refines the timeline of deer evolution, particularly the origin of crown deer and the relationships within Capreolinae.
• The findings contribute to a clearer understanding of cervid diversification and evolutionary history.