WWD: Diplodocus hallorum (Adult)

And here we start moving on to the next episode in the series, with the main protagonist species, Diplodocus. Because the episode features mostly animals from the same geological formation, there's not much that needs to be changed, species-wise, although their appearances have been revamped to fit with modern knowledge. 

So, let's start off. In WWD, the Diplodocus is depicted as being able to reach over 40 metres in length, despite good remains of the genus at the time only confirming animals of up to 26 metres in length. However, the companion book gives the probable explanation that the huge size in the episode is based on Seismosaurus, which was suggested to be a species of Diplodocus. In this respect, it was ahead of its time, as Seismosaurus was indeed synonymized with Diplodocus later on, as D. hallorum (although there is some debate whether or not it's synonymous with the type species D. longus, a debate complicated by the fact the D. longus holotype is fragmentary garbage), but the massive given length of 45 metres was not (although initial estimates were even bigger, at up to 52 metres!). The vertebrae in the original specimen had been misplaced, throwing off size estimates; the actual size of the animal was "only" about 28-32 metres. Regardless, this (probably) isn't a Liopleurodon situation, as the contemporary diplodocid Supersaurus is believed to have reached over 40 metres.

Anyway, the primary difference here is the posture of the neck. At the time, it was thought that Diplodocus and other sauropods were unable to lift their necks much higher than their shoulders (with the grey area of brachiosaurs, which were certainly holding their necks vertically, not explained), but this has been heavily contested since then, with the studies that determined the neutral posture criticized for false assumptions on vertebrate neck postures. It seems more likely now that most, if not all, sauropods had necks that sloped upwards, as virtually all modern amniotes hold their necks at a more inclined position.

Although harder to see, another error was giving them elephantine feet. This is an extremely common error involving portrayals of sauropods, giving them way too much fat on their foot pads and too many claws. However, most sauropods either had only one or zero claws on their forefeet, and three claws on their back feet, and their front feet left horseshoe-shaped prints, as there was no "pad" at the back. Another mistake with the series' sauropods was putting nostrils on their forehead, which was the common practice back in the 20th century because this is where the bony nares were, but it fell out of popularity scientifically following research that suggested the much more likely possibility that the nostrils were near the end of the snout as with nearly all other reptiles, and were connected to the forehead nares by soft tissue. And speaking of soft tissue, well-preserved sauropod skull tissues have found some, perhaps most, sauropods had beak-like lips covering their mouths, rather than the protruding teeth seen in WWD.

The keratinous spines in both this and the original portrayal are largely speculative. They're based on a fossilized diplodocid tail of exceptional quality with large spines present, although they probably did not belong to Diplodocus itself, and whether they were present in an unbroken row along the entire tail, back, and neck, like an iguana's spines, is unknown.