While Tohl Narita got involved in the production of Ultra Q as the kaiju designer, it’s not that he got to design any monsters he liked all the time.
I assume that the hectic shooting schedules in the later stages of each series might have, conversely, enabled him to design monsters of his own accord to some extent.
Because, presumably, they couldn’t afford to spend a great deal of time discussing the issues on kaijus carefully though it’s just my guess.
In the early stages, however, directors’ intentions appear to have been reflected rather strongly in producing kaijus.
As to Garamon and the SFX director Toru Matoba for the episode, for example, some of Matoba’s ideas are likely to have been incorporated into the meteorite monster.
While it’s known that Narita designed Garamon’s face after a fish such as a species called kochi shown from the front in a photo by attaching a dog-like nose to it, it’s also explained that a photo of kasago was shown by Matoba to Narita.
Matoba seemingly states that he applied unique movements to Garamon after behavioral gestures performed by a popular baseball player, Shoichi Kaneda, back then.
According to Tetsuo Kinjo, the main screenwriter of the series, in his writing, he initially came up with an idea featuring a skeleton-like kaiju for the episode.
The skeleton-like features found in the shape of Garamon’s hands, legs and tail should be the traces of the idea.