Doting Dinosaur Dads?

Today, Sunday 19th June, is Father’s Day in the United Kingdom, a day to celebrate dads and fatherhood.  This led team members at Everything Dinosaur to discuss whether there was any evidence to suggest that male dinosaurs made good parents.  We suspect fishing trips and long walks down by the river were not part of being a father for the Dinosauria (although one could excuse us the thought that some baryonchids, as fish-eaters, might have indulged in this), but is there any evidence in the fossil record to support the hypothesis that males helped raise their young?  Has palaeontology shed some light on whether or not male dinosaurs assisted in raising a family?

Surprisingly, a number of research papers have been published that explore the evidence to see if male dinosaurs were doting dads.

Did Dinosaurs Make Good Dads?

Did dinosaur males play an active role in looking after the nest?

Picture credit: Gabriel Lio

Modern Birds Can Provide a Clue

By looking at the parental behaviours of modern birds, scientists can perhaps get an insight into the parental behaviours of members of the Dinosauria.  For example, in extant birds (neornithes), the male parent sits on the nest and incubates the eggs in around 90% of species.

Scientists from Montana State University examined the fossilised bones of three different types of Cretaceous theropod dinosaurs, fossils of which had been found in association with nests of their own kind.  The dinosaurs in question, the troodontid Troodon formosus along with two oviraptorids Oviraptor philoceratops and Citipati osmolskae showed no evidence of medullary bone in the fossils.  In order to produce eggshells, females need a source of phosphorous and calcium.  These minerals are sourced from their own bones.  Specialised tissue is formed inside the bones during female ovulation.  This bone (called medullary bone), provides the minerals for the eggshells.

Once egg laying has finished then this tissue is reabsorbed but it leaves clearly identifiable cavities in the bone for some time.  If these cavities are detected in fossil bone, then this is a strong indication that the bones you are studying are from a girl.

Medullary Bone Identified in a Tyrannosaurus rex

Medullary bone identified in Tyrannosaurus rex femur.

Picture credit: Scientific Reports

Studying Bones of Theropod Dinosaurs

The Montana State University team looked at the theropod dinosaur bones in a bid to find the tell-tale medullary cavities, they found none and concluded that the fossil bones associated with the dinosaur nests were probably male.  It could be assumed that close association with the nest and eggs indicated some role in the brooding process, parental behaviour from a daddy dinosaur.

For models and replicas of theropods and other dinosaurs: Beasts of the Mesozoic Models.

Commenting on the conclusions drawn from this 2008 study, one of the researchers Dr David Varricchio explained:

“Paternal care in both troodontids and oviraptorids indicates that this care system evolved before the emergence of birds and represents birds’ ancestral condition”.

Difficult to Infer Behaviour from the Fossil Record

A number of scientists have challenged the conclusions drawn from this research.  It is difficult to infer behaviour from, what is a highly fragmentary fossil record.  For example, other papers have assessed the size of dinosaur egg clutches and compared them to living birds to see if further clues about parental responsibilities amongst the dinosaurs could be inferred.  How dependent hatchlings were from birth is also a factor to be considered.  A study from the University of Lincoln undertaken in 2013, suggested that most theropods exhibited precociality (hatchlings are born relatively mature and exhibit a high degree of independence from their parents).

To read more about the University of Lincoln research: Doting Dinosaur Dads Might Not be the Case.