Casey M. Holliday


Research Interests

Vertebrate Functional Morphology & Evolution



3D Alligator- Adult Skull 


Alligator mississippiensis is North America’s model crocodilian species and offers numerous insights into the evolution and functional anatomy of this group of reptiles, as well as their relatives such as lizards, dinosaurs, and birds. Three-dimensional visualization methods have moved to the forefront of comparative and evolutionary anatomy during the past decade. The head, being the intersection of numerous organ systems, has featured prominently in many studies. However, the complicated nature of reptile and particularly crocodilian heads has not been thoroughly illustrated using many of these 3D techniques. Sites like UTCT's Digimorph and OU's WitmerLab have made major headway in disseminating 3D anatomy of crocodilians, and we hope to add to this growing resource.

Here, we present a 3D, web-based anatomical atlas of Alligator cranial anatomy, which includes data from CT imaging techniques of an adult alligator. One head of a large alligator (Holliday Lab# AL022) was CT-scanned then imported into Amira (v5.2, Visage Imaging) segmentation software. We selected and highlighted individual skull elements using their sutural boundaries and created .stl files. These files were then converted into Java-based interactive models using Adobe Acrobat 3D and WireFusion. Corel X, Quicktime Pro and other software packages were also used to generate additional images and movies.

The centerpiece of the page is a virtual, dissectible Alligator skull where each individual bone can be explored in a 3D environment using a 3D PDF. Moreover, each element has a dedicated page with a WireFusion model, labeled images, and a brief description.

We have partnered with the WitmerLab on the 3D Alligator page. Here we host a model of the skull elements of an adult Alligator, whereas you can find equally stellar models and movies of juvenile alligators at the Witmerlab's 3D Alligator sister site.

The 3D database of cranial bones presented below is largely due to the efforts of Mizzou Life Sciences Hughes Fellow and Undergraduate Rebecca J. Skiljan. With her expertise in modeling and croc anatomy, Becci is now conducting a project investigating feeding functional morphology in a fossil crocodilian.

In the near future, we will be hosting additional models of crocodilian data generated by the Holliday Lab including models of Alligator jaw muscles, mandibular symphysis, trigeminal nerve as well as data from other ongoing extant and fossil crocodilian projects.  These data and their models are generated from not only medical CT such as the 3D Alligator here, but also microCT, MRI, and microMRI, as well as histology and dissection.

Comments, ideas for additions, and questions can be directed towards the 3D Alligator's blog page.

Acknowledgments: Thanks to Henry Tsai, Ian George, Jong-In Kim, Cortaiga Gant for contributing and aid during the projects development. We thank Ruth Elsey at Rockefeller State Wildlife Refuge, LA for Alligator specimens, the Brain Imaging Center at Mizzou for MR-Imaging, Cabell Huntington Hospital, WV for medical CT scanning, the Biomolecular Imaging Center at Mizzou for microCT and microMRI, and input from Lawrence Witmer (Ohio University) and Leon Claessens (Holy Cross). Funding was provided by University of Missouri Research Board Grant CR000305, Mizzou's CASH program, Mizzou's Program in Integrative Anatomy, and the Department of Pathology and Anatomical Sciences.

Above: examples of previous dissemination of Alligator cranial anatomy.

Below: Mizzou Undergraduate Rebecca Skiljan and the 3D Alligator Project


3D Database of the cranial bones of the American Alligator (Alligator mississippiensis)

Download 3D pdf of Half-Alligator :

High Resolution PDF


Low Resolution PDF

Download Quicktime movies of Half-Alligator





Download Undergraduate Rebecca Skiljan's poster from Mizzou's Life Sciences Research Day, April 2011


Individual pages for Adult Alligator Cranial Elements

Click on element's name to open dedicated page

Element's location in skull Picture of element

Click on element's name to open dedicated page

Element's location in skull Picture of element
Angular Palatine
Articular Palpebral
Basioccipital Parietal
Basisphenoid Postorbital
Coronoid Prefrontal
Dentary Premaxilla
Ectopterygoid Prootic
Exoccipital Pterygoid
Frontal Quadrate
Jugal Quadratojugal
Lacrimal Splenial
Laterosphenoid Squamosal
Maxilla Stapes
Nasal Supraoccipital
Hyoid  Surangular