Although the Tropidostoma Assemblage Zone, from where Bulbasaurus hails, is named after the oudenodontid Tropidostoma, Tropidostoma is only the third most common dicynodont in this assemblage zone.
Most common is the small Diictodon, over 2000 specimens of which are known from the Tropidostoma AZ alone.
Also more common than Tropidostoma is Pristerodon.
Other dicynodonts present include Cistecephalus, Dicynodontoides, Emydops, Endothiodon, Oudenodon, Palemydops, and Rhachiocephalus.
Notable in the Tropidostoma AZ is the lack of geikiid and dicynodontoid dicynodonts (Dicynodontoides is a diictodont), which is unusual since they must have already diverged from their ancestral lineages by this time; Bulbasaurus happens to fill the former gap.

The Tropidostoma AZ also records the gradual diversification of therocephalians and gorgonopsians.
Therocephalians present include Hofmeyria, Ictidosuchoides (most common), Ictidosuchops, Ictidosuchus, and Lycideops; gorgonopsids present include Aelurognathus, Aelurosaurus, Aloposaurus, Cyonosaurus, Gorgonops (most common), Lycaenops, and Scymnognathus.
Within the Karoo Supergroup, cynodonts also first appear within the Tropidostoma AZ; they include Abdalodon (formerly assigned to Procynosuchus) and Charassognathus.
Rarer members of the Tropidostoma AZ assemblage include the burnetiamorphs Lobalopex and Lophorhinus; parareptiles Pareiasaurus and Saurorictus; the archosauromorph Younginia; and the temnospondyl Rhinesuchus.

Bulbasaurus was probably buried on floodplains surrounding a meandering river up to 350 metres (1,150 ft) wide and with point bars up to 3 kilometres (1.9 mi) in diameter.
This river flowed from the southern mountains northeast onto an alluvial fan some 500 kilometres (310 mi) wide.
The water flow in the rivers was seasonally dependent, but there was probably flowing water year-round.
About every 30,000 years, the river banks were breached by flooding, leaving overbank deposits and a series of small, isolated ponds.
Although the Tropidostoma Assemblage Zone, from where Bulbasaurus hails, is named after the oudenodontid Tropidostoma, Tropidostoma is only the third most common dicynodont in this assemblage zone. Most common is the small Diictodon, over 2000 specimens of which are known from the Tropidostoma AZ alone. Also more common than Tropidostoma is Pristerodon. Other dicynodonts present include Cistecephalus, Dicynodontoides, Emydops, Endothiodon, Oudenodon, Palemydops, and Rhachiocephalus. Notable in the Tropidostoma AZ is the lack of geikiid and dicynodontoid dicynodonts (Dicynodontoides is a diictodont), which is unusual since they must have already diverged from their ancestral lineages by this time; Bulbasaurus happens to fill the former gap.
The Tropidostoma AZ also records the gradual diversification of therocephalians and gorgonopsians. Therocephalians present include Hofmeyria, Ictidosuchoides (most common), Ictidosuchops, Ictidosuchus, and Lycideops; gorgonopsids present include Aelurognathus, Aelurosaurus, Aloposaurus, Cyonosaurus, Gorgonops (most common), Lycaenops, and Scymnognathus. Within the Karoo Supergroup, cynodonts also first appear within the Tropidostoma AZ; they include Abdalodon (formerly assigned to Procynosuchus) and Charassognathus. Rarer members of the Tropidostoma AZ assemblage include the burnetiamorphs Lobalopex and Lophorhinus; parareptiles Pareiasaurus and Saurorictus; the archosauromorph Younginia; and the temnospondyl Rhinesuchus.
Bulbasaurus was probably buried on floodplains surrounding a meandering river up to 350 metres (1,150 ft) wide and with point bars up to 3 kilometres (1.9 mi) in diameter. This river flowed from the southern mountains northeast onto an alluvial fan some 500 kilometres (310 mi) wide. The water flow in the rivers was seasonally dependent, but there was probably flowing water year-round. About every 30,000 years, the river banks were breached by flooding, leaving overbank deposits and a series of small, isolated ponds.
Bulbasaurus