Background info

There is a planet on which all dinosaurs can survive. Aliens have transported at least 2 M-F pairs of dinosaurs from the Triassic, Jurassic, and cretaceous time periods.

A T rex pack has an Allosaurus egg in their nest that they will take care of along with 5 baby T rexes.



Length: 38 feet

Height: 16.5 feet

Weight: 1.4 tons

T rex:

Length: 40 feet

Height: 15-20 feet

Weight: 6-7 tons(as much as an elephant)


I know some people are going to say "Obviously not since they lived in different time periods."

However like I said in the background info, on this fictional planet Allosaurus and T rex live at the same time.

So the question is:

Could Allosaurus breed with T rex to produce fertile offspring since both are theropods and would have similar DNA? There have been some cases of successful hybrids of animals in different genera(How else could a pumapard(hybrid between leopard and puma) exist?) as well as interspecies hybrids and hybrids of subspecies.

From the characteristics it looks like it would most likely be a male T rex breeding with a female allosaurus.

However dinosaur mating is not very well known. It could be like how lizards mate or it could be completely different.


closed as off-topic by anon, sphennings, Bellerophon, Mołot, Frostfyre Dec 11 '17 at 19:13

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about worldbuilding, within the scope defined in the help center." – anon, sphennings, Bellerophon, Frostfyre
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ They can't see very well and both use different body odors, i guess since they can't high three they will then try to consume each other rather than consummate their lust! $\endgroup$ – user6760 Mar 31 '16 at 6:35
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    $\begingroup$ They could, but only if they have good communication and really believe in each other. $\endgroup$ – Liesmith Mar 31 '16 at 7:39

No They Could Not, And Here Is Why

If our current knowledge about the classification of dinosaurs is correct, then no, Allosaurus couldn't mate with T. Rex even if both lived in proximity.

The reason for this is that Allosaurus belongs to Carnosaur group of predators (which contains African and South American predators such as Carcharodontosaurus and Giganotosaurus) while T. Rex belongs to Tetanurae group (which contains raptors, birds and other feathered beasts).

You can say that if Allosaurus is modern day polar bear, then T. Rex would be jaguar. Both are carnivores, both are mammals, both live at the same time, but a polar bear cannot mate with a jaguar even if you keep them both in the same cage for years and years.

Should You Really Care If They Couldn't?

The real question should not be whether Allosaurus count mate with T. Rex but do you want to have that in your story/movie/game?

If you want to do that, you don't need to find excuses for that. Just do it. Your readers/viewers would know that you are writing science fiction and not a scientific article or documentary. So as long as the plot is interesting and fun to read/watch, it's all cool.

Heck! When Jurassic Park 4 could have a 40 feet high, camouflaging, thermal sensing monster (actually it would be extremely hard to even get a 40 feet high predator work at all!), your idea is much more believable and fun!

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    $\begingroup$ I particularly liked the JP4 mention :P $\endgroup$ – frarugi87 Mar 31 '16 at 13:23
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    $\begingroup$ +1 thank you for painting the large genetic divergence between the species. I would have been less descript $\endgroup$ – anon Dec 11 '17 at 16:40

T. rex and Allosaurus are both theropods, but they're members of completely different families--Tyrannosauridae and Allosauridae. I don't know very much about genetics or taxonomy, but the first comparison that comes to mind is a dog mating with a cat. Canidae and Felidae are both in the same order, but they're completely different animals and wouldn't be genetically compatible.

As far as I know, the false killer whale and the bottlenose dolphin are the only known animals capable of producing fertile hybrids across genera, and even then their offspring rarely survive into adulthood. And those are two animals in the same family.

I do think it's possible that a T. rex might care for a baby Allosaurus as if it were its own. Lots of animals "adopt" members of different species for some reason.

  • $\begingroup$ Another example if interbreeding genera: see this Question. I never got an answer, BTW. $\endgroup$ – JDługosz Mar 31 '16 at 12:21

No. Allosaurus and T. Rex may look superficially similar, but they're separated by close to 100 million years of evolution. Genetically, they were probably significantly more different than humans and chimpanzees.


Breed may be defined as having fertile offspring, or simply offspring.

Consider the mule, generally infertile offspring of a donkey and a horse. Ligers, on the other hand, may be fertile. So if you are screwing with the natural evolution of your planet enough to make Allosaurus and Tyrannosaurus contemporaries, feel free to make them related closely enough. Just don't call it ...


Dinosaur genetics is not crazily different from bird genetics and mammal genetics... Humans currently could still mate with neanderthals who are different form us by about 800.000 years of evolution, i.e. 34000 generations... I'd say that's quite a high limit on maximum generations of an advanced vertebrate between mating, it depends how fast the creature evolves, birds and reptiles do actually evolve rather fast in between generations same as mammals. Biologically speaking, that's a fair estimate of the kinds of limits of generations in prior to total species division of advanced vertebrates, 50k generations, 100k even.

Interesting to know: Crocodiles are very slow changing dinosaurs, there are dinosaurs from 110 million years ago that are nearly the same as today, we can suppose that speciation of dinosaurs can take many millions of years. Along with pterosaurs and dinosaurs, crocodiles were an offshoot of the archosaurs, the "ruling lizards" of the early to middle Triassic period (needless to say, the earliest dinosaurs and the earliest crocodiles resembled one another a lot more than either resembled the first pterosaurs!). What distinguished crocodiles from the first dinosaurs was the shape and musculature of their jaws, which tended to be much more deadly, as well as their relatively splayed limbs (as opposed to the straight, "locked in" legs of theropod dinosaurs).

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    $\begingroup$ Note that "evolution" is a phenomenon which occurs in populations over a span of generations and does not apply to individuals or populations over the course of a single generation. "Genetic mutations" occur at the individual level, however this only affects populations in evolutionary terms through heredity over many generations (assuming that the mutation is not fatal and is propagated over time such that its presence can be measured in a representative sample of the population). So technically nothing "evolves" from one generation to the next, but mutations may occur between generations. $\endgroup$ – Nolo Mar 31 '16 at 6:04
  • $\begingroup$ Yes indeed, isolated groups of animals evolve over a prolonged time span of many hundreds, and almost always thousands of generations. Evolution of the species is scientific, and evolution of animals less scientific and more popular semantics. Reptilians have been know to stay morphologically the same for many millions of years, i.e. Nile crocodiles are related to early triassic pterausaurs with splayed limbs and more simple and deadly jaw construction, and are the least evolved in 65 million years, however T-Rex was much closer to the bird family and more blood temperature regulation. $\endgroup$ – predatflaps Mar 31 '16 at 7:38

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