Yale Peabody Museum Summer Internships
Figure 1. A) The stem archosaur Euparkeria; B) the stem crocodile Simosuchus; C) the early dinosaur Herrerasaurus; D) juvenile of Dromaius; E) the non-avian dinosaur Majungasaurus.

The deep origins of the skull in the bird/crocodile lineage

Advisors: Prof. Bhart-Anjan S. Bhullar, Matteo Fabbri and Adam Pritchard

bhart-anjan.bhullar@yale.edu, matteo.fabbri@yale.edu, adam.pritchard@yale.edu

Length: 8-10 weeks in the summer

 

Project Description:

Archosauria is the most diversified tetrapod clade present today, including 24 species of crocodiles and 10,000 species of birds.  The fossil record provides the opportunity to track the transition from early stem archosaurs to modern birds and crocodiles, looking at morphological traits and occasional preservation of soft tissues. However, many questions regarding this transition are still open and lack a clear answer.

 

We propose a project that will include a morphology-based evolutionary perspective to elucidate the major novelties in the archosaur skull including fossil stem and extant crown archosaurs. The main focus of this project will be the evolution of the central nervous system and skull in Archosauria. Examples of important shifts in skull morphology in Archosauria are the loss of teeth, the gain of a rhamphotheca, loss of bones in the skull (e.g. the post-parietal), elongation or shortening of the snout, enlargement of the eyes and the brain and successive expansion of skull roof and rearrangement of the cranial musculature. Previous studies regarding the major changes and novelties appearing in the archosaur skull focused mainly in the transition from non-avian dinosaurs to birds. Moreover, statistical analysis performed on the reported datasets were often limited to 2D morphometrics, leading to a simplification of the 3D skull shape.

 

We are planning to pursue the first comprehensive study of the evolution of the archosaur skull and brain based on 3D CT scan data. The study will include pivotal taxa ranging from the basal most branches of Reptilia, and including both crocodile- and bird-lineages (Figure 1 (at right). A) The stem archosaur Euparkeria; B) the stem crocodile Simosuchus; C) the early dinosaur Herrerasaurus; D) juvenile of Dromaius; E) the non-avian dinosaur Majungasaurus. This list of taxa here illustrated already suggest the dramatic changes happening through the evolution of crocodiles and birds from the stem archosaurs, such as Euparkeria, and listed in the main text. The red dots in E represent the landmarks that will be placed on the CT scan data (in this case, placed on the skull of Majungasaurus), in order to perform 3D geometric morphometrics analysis. Scale bars equal to 10 mm in A-D and 10 cm in E.).

 

Developmental and ontogenetic series of extant taxa will be included in the analysis, in order to determine and better understand heterochronic shifts and differential patterns of ossification of the skull between the crocodile and bird branches. The inclusion of embryos will give new insights both from a developmental and evolutionary perspectives. Model taxa for the latter analysis will include alligator and chicken.

 

Given the novelty of the study and the approaches that will be used, the resulting paper will be submitted to a high-profile journal. The student will be one of the major authors in the paper. Moreover, the segmentation of the skull elements of some of the taxa included in the study will lead to further re-description of pivotal taxa that require further attention in the light of more recent discoveries in the field of paleontology. The student who will undertake this internship in our lab will be included as a coauthor in the papers focused on the re-description of these important taxa as well. The student will also gain confidence with specific software that will be used to pursue the analysis, and basic protocols aimed to the treatment of embryos, such as immunostaining and imaging techniques. Previous work by the lab on this topic has been reported in online, radio, and print news sources like NPR, BBC, and The New York Times.

 

Budget:

Stipend for lodging, food, etc.

$2500 ($3125 if 10 weeks)

TOTAL

$2500 ($3125 if 10 weeks)

 

CLICK HERE to apply!