coyotes can do ‘puppy dog eyes’ too: comparing interspecific variation in Canis facial expression muscles

Facial expressions are critical for non-verbal communication. The Canis genus epitomizes the interplay between behavior and morphology in the evolution of nonverbal communication. Recent work suggests that the levator anguli oculi medialis (LAOM) muscle is unique to dogs (Canis familiaris) within the Canis genus and evolved due to domestication. The LAOM raises the inner eyebrows, resulting in the ‘puppy dog eyes’ expression. Here, we test whether the LAOM is a derived trait in dogs by (1) examining the facial expression muscles of a closely related and ancestral wild Canis species, the coyote (C. latrans), and (2) comparing our results to other Canis and canid taxa. We discover that coyotes have a well-developed LAOM like dogs, which differs from the modified/absent LAOM in gray wolves. Our findings challenge the hypothesis that the LAOM developed due to domestication. We suggest the LAOM is a basal trait that was lost in gray wolves. Additionally, we find inter- and intraspecific vari..., Sample Collection. We opportunistically collected nine coyotes (5 males, 3 females, 2 unknown sex) and one dog (male, Australian cattle dog; Table 1) to examine their muscles of facial expression under Texas Parks and Wildlife scientific collections permit number SPR-1221-200. All but one of our coyote specimens (BU008) were collected in McClennan and Galveston counties, Texas. BU008 was donated from a sportsman in Fayette county, Texas.  The dog was donated from Central Texas Humane Society in Waco, Texas. All specimens were adults based on age estimates from tooth wear. Prior to the dissection, the head was separated from the body at the base of the occipital condyle. We took a small tissue sample from the tongue, ear, or temporalis for genetic analysis. All specimens were in good condition (i.e., fresh dead with little to no muscle decomposition) and kept frozen in a -20℃ freezer until dissection. 
Dissections. Specimens were dissected fresh without any chemical fixation. Prior to be..., , # Data from: coyotes can do ‘puppy dog eyes’ too: comparing interspecific variation in Canis facial expression muscles

[https://doi.org/10.5061/dryad.3j9kd51rk](https://doi.org/10.5061/dryad.3j9kd51rk)

Each folder contains scaled photographs of the coyote and dog specimens used in this study, labeled based on the specimen ID. Photographs are from dissections of the muscles of facial expression. Dissections were performed in a biosafety cabinet. 

## Description of the data and file structure

All photographs within a file are of the specimen identified in the file name. Images are raw photographs. In some photographs, anatomical structures are numbered to aid in identification.  

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