Hare Krishna!
All glories to Srila Prabhupada!
There are 8,400,000 species of living entities as stated in the Viṣṇu Purāṇa. Some of these species may exist on one planet and not on another, but in any case within all the planets of the universe-and even in the sun-there are living entities. This is the verdict of Vedic literatures.
Out of this, human species are 400,000. Out of that, there are many uncivilized men. They are almost like animals. Then there is civilized form of human being, just like we are. Many of them do not know what is spiritual life. Very few are interested in following spiritual life. So basically 400,000 human species indicates the levels of consciousness of different human beings present.
In the 8.4 million species, a large number of reptiles species are talked about, including gigantic size reptile, which is what our modern science calls as dinosaurs, so in that sense the existence of the dinosaurs is compatible with our scriptures. At the same time, it is not that the archaeologists have found extensive fossils of dinosaurs in every of the world by which they can claim that the dinosaurs were everywhere. But that is speculative hypothesis, which involves taking some small pieces of evidence and extrapolating, far beyond what the evidence warrants. Even if we believe that dinosaurs existed before on earth and now we can no longer see them, from a Vedic perspective all the 8.4 million species always exist. They may or may not be present on a particular planet, so they have actually not become extinct. Our scriptures mention so many big reptile creatures like Aghasura, Makara, Timingila, etc which we may not have seen but they do exist in other planets.
Also mule is not a new species. It is included in the 8.4 million species. Srimad Bhagavatam has several mentions of mule. For eg –
SB 3.10.23:
kharo ’śvo ’śvataro gauraḥ
śarabhaś camarī tathā
ete caika-śaphāḥ kṣattaḥ
śṛṇu pañca-nakhān paśūn
The horse, mule, ass, gaura, śarabha bison and wild cow all have only one hoof. Now you may hear from me about the animals who have five nails.
In conclusion, let us understand that our senses are imperfect and we have 4 defects. Modern world works by doing research with imperfect senses. However, in spiritual life all research is already done and there is no need to do further research. We simply have to accept the authority as started in our scriptures.