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Strange dinosaur adaptations; Who thinks these are plausible?
Topic Started: Feb 12 2010, 08:59 AM (8,959 Views)
Margaret Pye
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So, as I said on the introduction thread, I haz a maniraptoran sophont. I've been fleshing out a world for them to live in. And I've been violating the phylogenetic bracket appallingly - in ways that strike me as plausible, but I've been doing it a lot and I wanted some second opinions on the plausibility of some of my critters.

I've put fur on a lot of ornithopods, but that doesn't violate the phylogenetic bracket since Tianyulong. (I was writing furry ornithopods before Tianyulong, mind you - how else would Leaellynasaura have avoided freezing into a little hypsilophodont icypole? Especially since it didn't have growth rings in its bones, and therefore probably didn't hibernate.)

Things I want criticism and suggestions on, mostly dinosaur-related:

Opposable digits. I've been handing out opposable digits like candy, and with blithe disregard for phylogeny (I figured they could evolve repeatedly and independently.) Bipedal browsers get opposable digits with which to hold browse. Most of my small-game hunting coelurosaurs have hands like three-fingered hawk claws. Most of my grazers evolved from browsers, and most of my big-game hunters evolved from small-game hunters.

Direct brooding by a lot of ornithopods (I don't know what the ceratopsians and ankylosaurs do, I'll have to figure that out: I think sauropods are extinct, perhaps very recently as a result of sophont activity, and coelurosaurs are the only surviving theropods). No, there's no fossil evidence for it. But it seems enough of an improvement on the megapode model that I'd assume, given enough time, it could evolve. Is this stupid? (The obvious way to get round "It's too heavy to sit on eggs!" is to have them lie next to the eggs rather than on top.)

Pouches. I've given a lot of random dinosaurs (again, it seemed a simple enough and useful enough adaptation to evolve repeatedly and independently) some kind of skin pouch in which to incubate their eggs. A lot of the bipeds, including the sophonts, have "saddlebags" either side of the ribcage.

Venom. I have a clade of venomous coelurosaurs. In most of them, the venom is quite weak: it's the slashing sharklike teeth that do the real damage, and the vasodilator, anticoagulant venom just makes the wound bleed more so that the prey collapses faster. (Yep, idea stolen direct from Komodo dragon.) I'm thinking about creating some with more powerful venom, and possibly with a fancier venom delivery system than "it's in the spit so it gets all over the teeth." In particular, I was thinking about cheetahs, and I came up with a concept for a Coelophysis-shaped creature adapted for camouflage, stalking and incredible sprinting abilities. Except when it caught up with its prey, instead of wrestling it, it'd bite it once and let go - and the prey would run for another minute or so, then drop dead.

External ears. Yes, on dinosaurs. Specifically, on troodonts. Troodonts seem to have had very sensitive hearing, and asymmetrical ears like owls, so it seems reasonable to give them an external sound-focussing device. And yes, I could just give them an owly facial disc of vaned feathers, but external ears didn't seem that improbable. They aren't complex. They're strategically placed flaps of skin, plus a bit of cartilage stiffening and, if you're feeling fancy, some muscle.

Asymmetrical external ears, obviously. One pointing up, one sideways.

And a non-dinosaurian issue: I want to replace rabbits and hares with bipedal saltorial versions. Do you think I'm better off with wallabies, or with very large jerboas?

(I also want some saltorial-biped mammalian predators and omnivores, most of them under 5 kg: they don't have to be related to the kangabunnies, and I don't know whether they're marsupials or rodents either.)
My speculative dinosaur project. With lots of fluff, parental care and mammalian-level intelligence, and the odd sophont.
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Margaret Pye
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Modern birds only have a pygostyle, and its attached muscles move the tail feathers rather than being used in walking. And didn't the more advanced therizinosaurs, and various other maniraptors, convergently move the leg muscles to attach to the pelvis instead?
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Carlos
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Quote:
 
Modern birds only have a pygostyle, and its attached muscles move the tail feathers rather than being used in walking


There are still tail vertebrae besides the pygostyle, even if they aren't many.

Quote:
 
And didn't the more advanced therizinosaurs, and various other maniraptors, convergently move the leg muscles to attach to the pelvis instead?


It is possible, but I have not heard of it
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Margaret Pye
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I definitely heard so from a fairly reliable source (might've been Gregory Paul)... something to do with why dromaeosaurs have back-slanted pubic bones. I'd better go and look it up.
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Toad of Spades
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I found a picture that looks similar to my extremely specialized blind cave theropod idea.

Just slim down the jaws to deinonychus-like proportions, add the feather/whiskers, and add heat sensing patches and pits.
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Margaret Pye
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The picture's nice, but I don't think theropods are a good evolutionary starting point - I think it'd be better to start from something ectothermic.
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The Dodo
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Would something like that be able to find enough to eat in a cave?
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Toad of Spades
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Everything about it is on the previous page. It'll explain a lot of things.
Edited by Toad of Spades, May 16 2010, 01:21 AM.
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Margaret Pye
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Does anyone think it's a good idea to expand on the semiheterodonty of tyrannosaurs? Create a minityrannid with vaguely mammaloid (although still regularly replaced) dentition?

I'm thinking long upper and lower "canines" - conical, not Spec-style sabreteeth - probably in groups of two or three to provide spares, used as the main weapons. Since the lower jaw fits inside the upper jaw, the upper "canines" will hang over the lower lip. Smaller fangs, perhaps flattened side to side, across the front of the mouth for biting meat. The back of the mouth can have the bone-crushing teeth - perhaps just short, very thick blunt fangs, or perhaps I should go the whole hog and use flattened durophagus molar-like teeth.

And maybe flatten the face a bit?
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Toad of Spades
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Sounds like a good idea I don't see why not. It looks like they were heading toward heterodonty anyway, and they might have become heterodont if they didn't go extinct.

As for the teeth, the teeth in the back of the mouth could be short and thick like the teeth in the rear of the jaw in crocodiles. The front teeth could be sharp, pointy, and chisel-like. The "canines" should be easy to do.

The jaws and face could be highly varied by prey and hunting style. It would also be interesting to see tyrannosaurs with short cat-like faces and heavy jaws that could pulverize rock.
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Margaret Pye
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On second thoughts, I'm ditching the facultatively bipedal, cursorial therizinosaurs. All therizinosaurs that move faster than a waddle now belong to this clade:

UNGUIORNIDAE

This strange therizinosaur clade, related to tsasaka, is highly successful across most continentS. Unguiornids are not only quadrupedal: they have hooves. In the hand, the long powerful middle metacarpal takes all the weight. The middle finger has been reduced to one phalanx shaped into a keratin-coated hoof (which points forward in relation to the animal, or sideways in relation to the hand). A few unguiornid species retain the thumb as a long claw projecting from the front of the leg, but mostly the thumb and third finger have been reduced to little functionless spurs on the inner side of the wrist. The back feet have a more conventional unguligrade design, with the two middle toes converted into cloven hooves and the side toes lost.

Apart from the feet, they’re a similar shape to miniature tsasaka, with round fat bodies and long flexible necks. Their legs are flexed and much more muscular, and while they’ve mostly lost their tails they do retain a pygostyle for attachment of display feathers.

Unguiornids range from 100-2000 kg. Most of them are grazers, with the same broad flat-ended beak as tsasaka, but some have taken secondarily to browsing. Nearly all of them are fast runners, relying on their speed to escape predators and only fighting back when brought to bay.

The iera, Niveunguis haemopennantus, is one of the few large animals to tough out the tundra winter. They’re stockier and slower than most of their relatives, with unusually large eyes, a particularly good sense of smell for use in the long, lightless winters, and enormous snowshoe hooves. Female iera are about 300 kg and are covered entirely in thick, shaggy white down, with long white tail plumes. Males are nearly twice that size. They’re still mainly white, but the fluffy tail feathers are bright scarlet, and they have a long erectile scarlet mane all the way down the back of the neck.

Iera live in nomadic, non-territorial groups based around one male and a small harem of females: several of these groups can coexist peacefully in the same area if there’s enough food for them all. The spare males form loose flocks, often on marginal land. They’re usually the first to starve in winter or be eaten by Snow Queens.

Iera have been semi-domesticated, used for food and sometimes as beasts of burden, by many of the northernmost tribes.


My speculative dinosaur project. With lots of fluff, parental care and mammalian-level intelligence, and the odd sophont.
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Margaret Pye
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Abrachids

Tyrannosaurids have come down in the world rather badly. Several species survive, and some of them are even top predators, but none of them are over 100 kg.

All surviving tyrannosaurs belong to the clade Abrachia. This clade’s most distinctive features are the complete absence of forelimbs – even the shoulder girdle is missing – and the specialised heterodont teeth. They also run to very long, flexible tails and dramatic sexual dimorphism.

The teeth are regularly replaced and don’t conform to a strict dental formula, but they’re obviously specialised. The front teeth are short, close together, and flattened front to back, used by nibbling meat off carcasses. “Canines” form the main weapons – long conical fangs on either side of the front of the mouth, often long enough that the upper ones hang over the lower lip. Since the canines are frequently lost and replaced, two or three grow side by side to ensure spares. Teeth behind the canines are broad, flattened and durophagus, used to break bones into swallowable chunks (the few abrachid species that don’t eat bones have reduced or lost their back teeth, and have only canines and incisors).

The Yarley, Abrachus aureus

These athletic little tyrannosaurs are naturally found across much of the eastern continent, though they’ve been exterminated over large areas. Depending on the race, males weigh 80-100 kg and females 50-70. Both sexes are mostly covered in coarse blond fur, apart from the scaly brown legs and black stripes on the last third of the tail. Females have black sculpted bone and keratin decorations on their face, varying with race – the northernmost forms have large horns over each eye and a plain snout, whereas A. a. cristatus has two large bone crests (often battle-scarred) extending to just above the nostrils. Males lack these. Instead, they have a ruff of long erectile black scales – up to a foot long in the healthiest and most dominant males – all round the head, and a crest of similar scales along the tail. Females have a fairly standard tyrannosaur head shape, whereas males have a shorter snout, longer canines and an even more powerful bite.

Female yarleys are territorial and tend to be social and cooperative, although they may be found alone. The adult males are solitary and nomadic, and females tolerate their presence only in the mating season. Both sexes are pursuit hunters that eat mainly medium to large ornithopods and varks (A/N: the word “vark” now refers to a hoofed quadruped), though they’ll occasionally take on better-armed prey (multiple female yarleys attacking a gouger looks like a bullfight: one distracts the dangerous front end and leaps out of the way at the last minute, while the others dash behind it and try to bite the thighs.) They also like fresh carrion, and will kleptoparasitise given half a chance. They can bite through and digest bones, and so they’ll often finish off more powerful predators’ leftovers.

Yarleys nest communally and directly incubate their eggs. Newborns are highly precocial, and follow along on hunts from birth (they’re not much help at first, and usually get left far behind, but they catch up: when they turn up at the kill after it’s been entirely eaten, as often happens, the adults will regurgitate food for them.) Well-fed females will start breeding at one year old, when they’re less than half adult size. Females stop growing at age four or five, and might live to be twenty if they escape hunting accidents, bloody territorial combat and starvation. Males continue growing for another few years, during which time they occupy a dominant position in the pack: then they grow the feather ruffs and are thrown out. Most males die soon after this, in fights or from starvation - only a few live to breed, and even they don't usually live long.
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The Dodo
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Seeing as they can hunt in packs, how smart would they be?
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Margaret Pye
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About the level of a wolf or a lion, I suppose.
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Holben
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I think you're exaggerating there... (although wolves are quite a bit more intelligent than lions). No dinosaur could evolve the kind of intellectual advantage given by even the limbic system.

All pack-hunting reptiles have very simple hierarchies, and even now we're learning more about mammal hierarchy. It's much more complex.

Oh yeah, and mammals naturally have better creativity/forethought.
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Margaret Pye
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"No dinosaur could evolve the kind of intellectual advantage given by even the limbic system."

The word "could" is wrong. No real, existing Mesozoic dinosaur actually had that kind of intellectual advantage, but what would stop them from hypothetically evolving it if they'd continued beyond the end of the Mesozoic? Several bird clades have managed mammalian and supermammalian levels of creativity/forethought, so I can't see what would stop tyrannosaurs from reaching the level of a passably bright mammal if selective pressures favoured complex behaviour.

(And what's a "pack-hunting reptile"? All I can think of is Parabuteo unicinctus, which I suppose is a reptile if you insist on using the term cladistically. No squamate or crocodilian hunts cooperatively. I don't know enough about Parabuteo to comment on its social life, which is a shame.)
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