"Small" theropod macropredators

[theropod]

Easy test for whether an animal you look at is more likely 0.3g or 0.3kg in mass:

Look at your animal. Does the volume of said animal seem to be smaller than that of a teaspoon? If it is not smaller, then it’s probably 0.3kg, unless it’s made of air, in which case it’s probably not an animal.

[dinosauria101]

^Thanks theropod, I do quite appreciate that.

[Infinity Blade]

The large hooked claws on the hands provide some clues regarding Archaeopteryx's diet. The evolution of such claws was not necessary for snatching insects. Could the claws have been used to catch larger prey? We have already discussed why (contrary to Zhou and Martin [1999]) the feathered raptorial fingers could grasp well enough to help grab items such as prey. Holtz (1994b) observed that the creature had many of the adaptations of a miniature dromaeosaur, including the large, laterally flattened hooked claws on the hands and feet, as well as a hyperextendible second toe and a tail with a hyperflexible base. These features suggest that, like dromaeosaurs, Archaeopteryx was a leap-and-pounce predator, able to capture large vertebrate prey.

Although Archaeopteryx had claws suitable for capturing prey, it lacked the array of serrated, blade-shaped teeth predators typically use to slice their victims' flesh. Its teeth are small, short, and widely spaced. The unserrated crowns are subconical, with recurved tips that are somewhat compressed mediolaterally, a sharp anterior cutting edge, a rounded posterior edge, and a base that is rounded in cross section (Howgate 1984a,b, Wellnhoffer 1988, L. Martin 1991, Elzanowski And Wellnhoffer 1996). There is a slight or modest constriction between the crown and root of each tooth, and the roots are slightly bulbous. Such teeth are suitable for grabbing or swallowing prey whole or for chopping up large items. In contrast, small insectivorous lizards tend to have larger, more closely spaced teeth with roots that continue straight into the crown (Hotton 1955), teeth that are suitable for piercing the hard but thin exoskeletons of arthropod prey.

Paul (2002)

[Infinity Blade]

The recently described Oculudentavis had a skull suggesting an animal around the size of a bee hummingbird. Or at the very least, a tiny theropod. It was a toothy predator, proposed by the author to have likely been a predator of small arthropods and other invertebrates. But the authors note something very interesting about its dental morphology.

Although unexpected for its small size, the large number of teeth—as well as their sharp and carinated morphology—suggests that Oculudentavis was a predator, probably feeding on small arthropods and other invertebrates (which are abundant in amber inclusions from the Angbamo site).

www.nature.com/articles/s41586-020-2068-4.epdf?referrer_access_token=do4fjBL9xFQ0pVGaqoSw_dRgN0jAjWel9jnR3ZoTv0P1uuDbeUktz-3Wk7vFlIN0uHPygK-kgIQFdft5m_6lFdQZ50wthHdddNGB1XF40sj_Ul8SiiFbxsiqJm2jZYwEw_aG0Mf0iouWumW83FsAB8zovesBLFpMGE8vKB9m5nV2us5HlYtwKSZUzoL62rZqrXsbWQHD7GvvT-eusjQ6wg%3D%3D&tracking_referrer=www.nationalgeographic.com

These teeth weren't just pointy, they had cutting edges on them, which suggests some ability to dismember prey. The rostrum was described as mesorostrine by the authors. I wonder if it was maybe hunting some tiny vertebrates too, and if so, how large these prey items were relative to Oculudentavis. At least Darren Naish has speculated such, wondering if it might be like some kind of tiny dinosaurian shrew.

Combined, what do these features tell us about the lifestyle and ecology of Oculudentavis? The well-fused skull, prominent teeth and large eyes suggest that this was a predator, presumably of small arthropods. The soft papillae on the palate are of the wrong sort for fish-eating (Xing et al. 2020). Its tiny size and forest habitat imply that it was arboreal or scansorial – as suggested by Gabriel’s artwork above – but the animals that surround it in the cladogram are mostly terrestrial, so the possibility that it foraged in leaf litter or took regular trips to the forest floor are also conceivable, perhaps. Could it have been a predator of worms, molluscs or even tiny vertebrates, like a dinosaurian shrew?

tetzoo.com/blog/2020/3/10/hummingbird-sized-archaic-birds-of-cretaceous

[Infinity Blade]

Juravenator starki seems like it would be relatively well equipped as a macropredator, judging from its teeth and claws. The excerpts and images down below are from Chiappe & Göhlich, 2010).

The three digits of Juravenator are robust and powerfully clawed (Fig. 20).

The arrows point to preserved keratinous sheathes of the claws.

The claw of digit II is much greater than the others and it has a prominent flexor tubercle. The proximal phalanx of digit III is distinctly longer than the other non-ungual phalanges of this digit. Its [digit III's] claw also bears a prominent flexor tubercle. Like in digit III, the proximal phalanx of digit IV is longer than the other non-ungual phalanges. However, the claw of this digit does not appear to carry a strong flexor tubercle.

The keratinous sheathes of the pedal claws are also preserved. The first of the two images directly above seems to suggest sharp tipped unguals, and the illustration of the remains confirms this. The digit II ungual is the largest, a condition seen in most extinct carnivorous non-avian theropods, and a likely adaptation for pinning prey (Fowler et al., 2011). The second and third pedal claws even have well-developed flexor tubercles.

Although all teeth lack mesial (front edge?) serrations, and the first premaxillary teeth lack any serrations at all, the rest of the teeth have distal (back edge?) serrations.

All preserved teeth (from both the upper and lower jaws) lack mesial serrations. The first preserved pre-maxillary tooth also lacks distal serrations but these are present in the second preserved premaxillary tooth (the third one is highly incomplete) (Fig. 10). Among basal coelurosaurs, serrated premaxillary teeth are known in the “compsognathid” Sinocalliopteryx (Ji et al. 2007a) and tyrannosauroids (Xu et al. 2004), although the premaxillary teeth of many basal coelurosaurs (and a number of tetanurans) lack serrations (OSTROM 1978; CURRIE & CHEN 2001). The serrations of the premaxillary teeth of Juravenator and Sinocalliopteryx are much finer (~ 13/mm) than those of the maxillary teeth (~ 8/mm). All other exposed teeth of Juravenator also have distal serrations.

Greg Paul in the Princeton Field Guide (p. 122; no preview available for this page on Google Books, I only know this because I have a downloaded PDF of it on my computer) seems to agree that this creature was eating fairly large prey.

Large teeth indicate it hunted fairly large animals; kink in upper jaw indicates it also fished. Prey included Archaeopteryx.

To be fair, though, the adult size of Juravenator seems to be uncertain, as Paul points out in the Princeton Field Guide. Only a single juvenile specimen is known. But even at this size Juravenator seems to have some pretty substantial adaptations for hunting (relatively, of course) large prey.

[Supercommunist]

In a hypothetical world where mustelids went extinct before modern humanity arose, I suspect paleontologists would have dismissed the notion that fishers are capable of preying on larger lynxes or that wolverines could kill adult reindeer as pure "awesome bro" fanboyism.

I am inclined to think that there were a bunch of small nasty theropods that could punch well above their weight.

[Infinity Blade]

The fact that Velociraptor was a thing should already be enough proof of that tbh. I'm still convinced that a couple of the examples I posted above (particularly Archaeopteryx and Juravenator, but also something like Sinornithosaurus) could have been suitable candidates for the "really nasty small predator that punches above its weight" description.

[Supercommunist]

I guess the thing with the fighting dinosaurs find is that the protoceratops doesn't look that much larger. IIRC it was a lot heavier but its not something that would really impress the average person.

I do find it weird that some people try to downplay the dromeosaurids big hunting abilties when they point out their sickle claws probably couldn't cut that well, and the retort is a big "and?"

As discussed in another thread, you want stabby claws because slashy claws are inherently less lethal weapons.

[razor45dino]

I don't really agree with that. Head alone looks comparable to the size of the raptor

Attachments:

[Supercommunist]

The average person is going to focus on total length rather than body proportions.

It's why people will always describe 6 or 7 foot long caimans as giant crocodiles when they actually are only about as heavy as woman.

[razor45dino]

that makes sense. I would guess most people just either haven't seen the fossil in person or have seen it in a perspective where the size difference isn't looking as big too.

I also think this whole "dromaeosaur downplay" is the result of people trying to counteract that whole awesomebro Jurassic Park popularized version of raptors and they basically go in the complete opposite direction even if their view literally does not make sense with all the evidence we have. It's definitely unfortunate.