What is less well known is that these Hong Kong toys were loosely modeled after kaiju from Ultraman (and other tokusatsu shows). The umber colored creature on the left is what is generally recognized as the inspiration for the umber hulk.
It is most likely that the umber hulk was derived from the kaiju known as Antlar (アントラー), but the Hong Kong toy does not bear much of a similarity to Antlar outside of the mandibles, and in fact looks more like Gomora/Gomora II (ゴモラ).
As a side note, Antlar and Gomora appear together in episode 4 of Ultra Galaxy Mega Monster Battle, so maybe the patchisaur was somehow derived from that episode.
The modern iteration of the umber hulk is more true to the original source material than the 1st ed. AD&D version of the umber hulk.
Here is a comparison of some of the 1st edition type umber hulks that I own.
To me, the Citadel (ADD77) version is ideal in terms of appearance and size for use with 1/72 scale fantasy. It really captures the appearance of the original Sutherland umber hulk. Next to the Citadel umber hulk, the Heritage Brawn Hulk (Dungeon Dwellers 1257) seems rather scrawny. It does not have any outer mandibles, and has a pebble textured skin. Perhaps it can be used as a vodyanoi. The last miniature is the Ral Partha umber hulk (AD&D Monsters 11-404). It has an armored carapace and mandibles, but the outer set of eyes is not very pronounced. It is more mesomorphic than hulkish, and is too tall for use with 1/72 miniatures.