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Yep! You are! You're only the second person I've seen who noticed it!

Overall, I am very happy with this project. I would like to sincerely thank my coauthors and many mentors and friends I've made along the way. I would also like to thank the guest editors of the special issue Mateusz Wosik and @funstonpaleo.bsky.social . I am excited to see the full thing!

It is worth noting however, that histological markers can vary a lot across the skeleton of an individual, so approach direct comparisons with other individuals and elements with caution. Always consider histological studies in the context of which bones were sampled and where

What this could mean we have no idea. Sexual dimorphism with different ages of reaching sexual maturity? Different taxa entirely with different growth trajectories? Something else? A Regardless, we found it extremely interesting and definitely something worth exploring

Stranger however, is that there appear to be two growth trajectories present even among the healthy individuals. One with an earlier growth spurt and plateau (blue, red, orange?), and another with a later one (teal, black, green)

We were curious how, (if at all), these pathologies impacted growth in these animals, so we measured area within cyclical growth marks. While it appears TMP1992.036.0720 (red) may have experienced reduced growth, the other two (black and teal) seem relatively unaffected

Unlike the other two specimens, the trauma in this one appeared to have happened earlier in life and was more widely impacting. Severe resorption at the distal end suggests chronic inflammation at the distal joint that may have resulted in lameness and subsequent injuries

The third specimen however, was a little bit more complicated. TMP1992.036.0720 consisted of a severely deformed MTIV (pictured here) and a slightly deformed MTII

Speaking of stress, we selected three pathologic specimens we deemed good candidates for histology. Two of these appear to have relatively straightforward conditions. A superficial cortical fracture, and an enthesophyte turned chip fracture in another.

By taking full cross-sections and sampling across the entire metatarsus, we were able to map where along the metatarsus different bone types occur, which parts grow and finish growing first, and where the stresses concentrate (as shown by Haversian bone)

Fortunately, metatarsals are among the most commonly found and recognized isolated troodontid elements from the Dinosaur Park Formation, and this combined with the generosity of the lovely folks at the Royal Tyrrell, allowed us to section 11 specimens!

So we set forth to sample as many metatarsals as we could in hopes of not only exploring the growth of troodontids from the DPF (which had never been done prior) but also to diagnose pathologies we found and see how they related to the animal's life stage or impacted growth.

My lovely colleagues Mark Powers and @a-dyer-wolf.bsky.social introduced me to the world of histology, and how it can be used not just to help diagnose pathologies like the one above, but also explore the life history of these animals (the first section we made shown here)

At the 2022 SVP meeting, I presented the preliminary findings of my metatarsal pathology survey, among which was an unusually high occurrence of pathologies in troodontids. This paired with their weird anatomy, was hard to ignore, so I decided this taxon warranted a closer look

In particular, I became fascinated with the troodontids and their unusual modified arctometarsus (pictured on the right), which features an enlarged MTIV and reduced, laterally compressed MTII for bearing the raptorial digit.

In 2019, I begun my histology and pathology journey at the Royal Tyrrell Museum surveying theropod metatarsals for signs of injury and disease. I was interested in theropod feet because of their similarity to those of birds, and metatarsals because of their varied morphologies

Paper here, thread following
onlinelibrary.wiley.com/doi/10.1111/...