The rather predictable Eustreptospondylus replacement, considering this is the only well-known theropod dinosaur taxa from the Kimmeridge Clay and roughly the same size as the original species (the hypothetical adult size of Eustreptospondylus at least), although it's changed from a megalosaur to a tyrannosaur. Although it should be noted that, unlike Eustreptospondylus, Juratyrant is not known from a skull, and the appearance here is largely speculative.
It would nonetheless play the same (speculative) role of a coastal predator and beach-combing scavenger. Although only a medium-sized carnivore of the time period, by comparison with modern land predators, it's only exceeded in mass by the very largest polar bears.
The episode presented Eustreptospondylus as being an insular dwarf and beach-combing specialist, but these are both purely hypothetical interpretations, and the former is probably untrue since other large dinosaur species are known from the same formation (in fact, the pilot episode showed it coexisting with cetiosaurs); Eustreptospondylus' supposed small size was more likely due to the fact the only specimen is of a juvenile. The same is true with Juratyrant, as large stegosaurs, megalosaurs, and sauropods are known from the Kimmeridge Clay as well.
Also, Eustreptospondylus didn't actually live at the time the episode is set, and it doesn't even have the excuse of being a former wastebasket taxon like the other anachronistic species.
Its portrayal in the episode was a bit duller than I've drawn it, and I've grown to dislike that of the series, that it uses many bland, brownish hues for nearly all its animals, and it's possibly at its worst with the Eustreptospondylus, which is an incredibly generic, uniformly greyish-brown theropod that's just recycled from the Allosaurus model. I took some inspiration from the more vividly repainted head puppet for the patterns just so it wouldn't look similarly dull.