Phylogenies—or evolutionary family trees—are used by palaeobiologists and evolutionary biologists to create visual representations of their hypotheses about how organisms are related. 

For example, phylogenetic trees allow palaeobiologists to ponder whether horses and tapirs are more closely related to each other than rhinos and tapirs (current wisdom suggests that rhinos and tapirs form a group). 

Diagram showing possible evolutionary histories for rhinoceroses, tapirs, and horses.
These simple phylogenetic diagrams illustrate two possible evolutionary scenarios among three living animals: rhinoceroses, tapirs, and horses. In the upper phylogenetic arrangement, tapirs and horses are depicted as being more closely related; in the lower, rhinos and tapirs share a closer evolutionary relationship. Image: Danielle Fraser © Canadian Museum of Nature

Phylogenies are reconstructed using special “characters,” which represent differences in the physical features of species. For example, if scientists wanted to make a phylogenetic tree of different types of pasta, they could use the following characters and character states: 

Character 1 – Pasta Shape: Character state 0 = straight (like spaghetti and rigatoni), Character state 1 = curly (like fusilli) 

Character 2 – Pasta Length: Character state 0 = short (like fusilli and rigatoni), Character state 1 = long (like spaghetti) 

Character 3 – Pasta Form: Character state 0 = not hollow (like fusilli and spaghetti), Character state 1 = hollow (like rigatoni) 

Character 4 – Skin: Character state 0 = smooth (like fusilli and spaghetti), Character state 1 = ridged (like rigatoni) 

However, real phylogenetic trees are based on more than four characters. 

Characterization of pasta shapes to illustrate how phylogenies are constructed. 
If pasta were fossils—and the product of biological evolution rather than cultural traditions—shape and surface texture could be evaluated to suggest that spaghetti and fusilli are more closely related to one another than rigatoni. Image: Danielle Fraser © Canadian Museum of Nature

Character states are most often determined for individual species based on observation of specimens in museum collections. But how are palaeobiologists continuing their phylogenetic work in the age of Covid-19? How are they developing phylogenetic hypotheses without access to museum collections? 

When scientists cannot personally view specimens at a museum, images become invaluable; these include photographs in publications, photographs provided by museum curators, and free-to-access 3D scans.  

Images of specimens, particularly newly described species, can be found with published papers. These images are often of high quality and can be used to observe and record character states for species. Here is a lovely example of a paper with excellent specimen images published in the open access journal PLOS ONE. 

Photographs of fossil skull of an extinct mammal.
Photographs of the skull of Masrasector nananubis, a recently named new species of carnivorous mammal belonging to an extinct group called the hyaenodonts. Published in a scientific paper made freely available online, this specimen in the collections of the Duke Lemur Center in North Carolina can be easily assessed for character states from anywhere in the world. (A) dorsal view, snout points left, (B) ventral view, snout points left. Catalogue number: DPC 11990. Image: © 2017 M. R. Borths, E. R. Seiffert (CC BY 4.0)

Dryad is a place where scientists voluntarily provide images and other types of data after publishing a study in a scientific journal. Some journals now actually require that data be uploaded to Dryad upon publication. 

Here is an example of CT scans on Dryad published alongside a study exploring the reconstruction of damaged specimens. This data can be used freely for scientific study, provided there is no financial benefit. 

MorphoSource provides an outstanding selection of 3D scans representing many species, including mammals and fish. Some are CT scans and others are surface scans. They are provided by museum curators interested in improving the accessibility of their collections, as well as scientists who have decided to publish their study specimens. 

Here is an example of a beautiful Dinictis skull from the Raymond M. Alf Museum of Paleontology in California that is available from MorphoSource. A reconstruction of this extinct cat-like carnivore is on display in the Fossil Gallery of the Canadian Museum of Nature. 

Palaeobiologists and evolutionary biologists are working from home to help slow the spread of Covid-19. But the study of specimens and development of phylogenetic hypotheses continue, due in part to the combined efforts of museum personnel and scientists who make their data accessible to the wider scientific community. Thanks to their hard work and willingness to share information, my students and I continue to leverage freely available images and data to study the evolution and ecology of fossil mammals.