Thank you Casey for this really interesting spotlight talk in our thematic session. The methodologies a d results here presented got me interested if I could apply them to the group I am researching in my PhD.
As said. Great talk!
Hello Casey , loved your talk , I have a few questions would you mind answering them ,
1.) How does DPR concentration vary across pursuit based predatory crocs (mostly marine) and ambush based predatory crocs and a follow up being , how does salinity affect DPR activity
2.) Does Osteoderm thickness and shape affect DPR and neuromuscular foramina positioning
3.)You mentioned that extant crocs have a highly pennate muscles , then can we infer that extant crocs have a higher metabolic rate /(biomass consumed )than extinct crocodilians to sustain this more efficient muscular apparatus .
Thanks! I don’t have great answers for you but here are some largely unfounded opinions:
1) We haven’t looked at DPR vs behavior but using Emily’s data or data like it, one might be able to get at it, need more specimens too. In general I think we’d need more clear behavioral/stimulus data to really sort out if there even should be a difference between ambush and pursuit. I suppose ambush crocs would want more sensitive faces to close a gap, since once pursuit starts, most senses can pick up stimuli from the situation given the sounds, smells, sights, vibrations of a predation event.
I’m not aware of relationships between DPRs and saltwater. If DPRs rely on vibrational stimuli, and vibrations are sensitive to substrate density, then perhaps you might expect differences with salinity. Alligator would be a good test here since they’re common in brackish water and even Atlantic Ocean water fairly frequently. But also.. I guess since Pacific Ocean water is saltier than Atlantic Ocean water (right?) might pacific crocs have different sensitivities or differently built ‘antennae’ to vibrations?? Could be! This line of reasoning might apply to warm vs temperate waters as well given water density differences relative to acoustics.
2) Osteoderms… not sure… I’m not certain of places where there is an osteoderm where there are also DPRs? Most DPRs are on the face and head (which lacks osteoderms) and then along the belly in crocodiles which also lacks osteoderms. I don’t remember seeing DPRs reported for the dorsal surface of the body where osteoderms are more abundant, but maybe people haven’t looked closely enough. NV foramina… I can’t think of any relationship between neurovascular foramina and osteoderm shape/size/thickness. I think most osteoderms have them as they have NV canals passing within them, but they aren’t 1:1 with all the dimples (I think). I can’t think of any published observations in this vein but it is an avenue worth study because there’s also some ideas about there about osteoderms being thermally regulatory, and if that’s legit, then you might predict osteoderms might track with climates or thermal-relevant behaviors or BMR, or osteoderm density/ shape etc.
3)I’m not sure pennation and metabolism (or at least metabolic rate) are particularly related. That would matter more if animals were using their muscles more via increased activity levels, not just the potential work output via pennation. Lots of animals of all sorts of BMRs have a mix of pennate vs parallel muscles. It’s really more of a continuum than two distinct bins. But let’s consider… some herbivorous notosuchian or hylaeochampsid might have beefy, pennate muscles to tackle processing vegetation (like other herbivorous reptiles and mammals), and spend significantly more time and muscle energy ‘chewing’ than your typical baurusuchid or other bite, fight and gulp croc… All that additional behavior of chewing might theoretically require, or result in, a slight higher BMR than a species that is ‘chewing’ less. Sure a predatory croc is going to pump out some high muscle forces for a short period of time, but I suppose that’s where lactic acid production and fatigue comes in as opposed to phylogenetically increased BMR. If perhaps, we found Baurisuchds to be long distances pursuit predators (hah!) like African Hunting dogs, then maybe we’d expect a comprehensive/phylogenetic trend in increased BMR. Meanwhile, I think we have a growing body of evidence that suggests today’s crocs are somewhat ‘colder’ or lower BMR than their ancestors (even within the Alligator family since the Paleocene)…so doesn’t help the hypothesis that increased pennation=increased BMR. Finally, we’re just suggesting that a way crocs could rescue bite force could be this wild pennation they have today…. But I’m not all that certain we have a great way of estimating or inferring pennation in fossil taxa so it’d be hard to test our hypothesis for the polarity of that character set. There are some indirect evidences like aponeurosis scars, maybe sensitivity analyses with musculoskeletal models? Hmmm good times.
Good questions! Thanks for coming to the talk!
Casey
Esta es una tienda de demostración para realizar pruebas — no se completará ningún pedido.
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4 thoughts on “SPOTLIGHT TALK: GREAT TRANSFORMATIONS IN CROCODYLIFORM EVOLUTION”
Thank you Casey for this really interesting spotlight talk in our thematic session. The methodologies a d results here presented got me interested if I could apply them to the group I am researching in my PhD.
As said. Great talk!
Thank you! Reach out if you want. Happy to help.
Casey
Hello Casey , loved your talk , I have a few questions would you mind answering them ,
1.) How does DPR concentration vary across pursuit based predatory crocs (mostly marine) and ambush based predatory crocs and a follow up being , how does salinity affect DPR activity
2.) Does Osteoderm thickness and shape affect DPR and neuromuscular foramina positioning
3.)You mentioned that extant crocs have a highly pennate muscles , then can we infer that extant crocs have a higher metabolic rate /(biomass consumed )than extinct crocodilians to sustain this more efficient muscular apparatus .
Thanks! I don’t have great answers for you but here are some largely unfounded opinions:
1) We haven’t looked at DPR vs behavior but using Emily’s data or data like it, one might be able to get at it, need more specimens too. In general I think we’d need more clear behavioral/stimulus data to really sort out if there even should be a difference between ambush and pursuit. I suppose ambush crocs would want more sensitive faces to close a gap, since once pursuit starts, most senses can pick up stimuli from the situation given the sounds, smells, sights, vibrations of a predation event.
I’m not aware of relationships between DPRs and saltwater. If DPRs rely on vibrational stimuli, and vibrations are sensitive to substrate density, then perhaps you might expect differences with salinity. Alligator would be a good test here since they’re common in brackish water and even Atlantic Ocean water fairly frequently. But also.. I guess since Pacific Ocean water is saltier than Atlantic Ocean water (right?) might pacific crocs have different sensitivities or differently built ‘antennae’ to vibrations?? Could be! This line of reasoning might apply to warm vs temperate waters as well given water density differences relative to acoustics.
2) Osteoderms… not sure… I’m not certain of places where there is an osteoderm where there are also DPRs? Most DPRs are on the face and head (which lacks osteoderms) and then along the belly in crocodiles which also lacks osteoderms. I don’t remember seeing DPRs reported for the dorsal surface of the body where osteoderms are more abundant, but maybe people haven’t looked closely enough. NV foramina… I can’t think of any relationship between neurovascular foramina and osteoderm shape/size/thickness. I think most osteoderms have them as they have NV canals passing within them, but they aren’t 1:1 with all the dimples (I think). I can’t think of any published observations in this vein but it is an avenue worth study because there’s also some ideas about there about osteoderms being thermally regulatory, and if that’s legit, then you might predict osteoderms might track with climates or thermal-relevant behaviors or BMR, or osteoderm density/ shape etc.
3)I’m not sure pennation and metabolism (or at least metabolic rate) are particularly related. That would matter more if animals were using their muscles more via increased activity levels, not just the potential work output via pennation. Lots of animals of all sorts of BMRs have a mix of pennate vs parallel muscles. It’s really more of a continuum than two distinct bins. But let’s consider… some herbivorous notosuchian or hylaeochampsid might have beefy, pennate muscles to tackle processing vegetation (like other herbivorous reptiles and mammals), and spend significantly more time and muscle energy ‘chewing’ than your typical baurusuchid or other bite, fight and gulp croc… All that additional behavior of chewing might theoretically require, or result in, a slight higher BMR than a species that is ‘chewing’ less. Sure a predatory croc is going to pump out some high muscle forces for a short period of time, but I suppose that’s where lactic acid production and fatigue comes in as opposed to phylogenetically increased BMR. If perhaps, we found Baurisuchds to be long distances pursuit predators (hah!) like African Hunting dogs, then maybe we’d expect a comprehensive/phylogenetic trend in increased BMR. Meanwhile, I think we have a growing body of evidence that suggests today’s crocs are somewhat ‘colder’ or lower BMR than their ancestors (even within the Alligator family since the Paleocene)…so doesn’t help the hypothesis that increased pennation=increased BMR. Finally, we’re just suggesting that a way crocs could rescue bite force could be this wild pennation they have today…. But I’m not all that certain we have a great way of estimating or inferring pennation in fossil taxa so it’d be hard to test our hypothesis for the polarity of that character set. There are some indirect evidences like aponeurosis scars, maybe sensitivity analyses with musculoskeletal models? Hmmm good times.
Good questions! Thanks for coming to the talk!
Casey