Theriosynoecum favus Almeida-Lima, Guzmán, Maia, Jesus & Piovesan, 2024, sp. nov.

Theriosynoecum favus sp. nov. (Fig. 4N–P; Fig. 5D) 2022 Theriosynoecum sp. —Guzmán et al., p.21, Fig. 13M–O. 2023 Theriosynoecum sp. —Guzmán et al., p. 27, Fig. 7M–N. Zoobank-link: urn:lsid:zoobank.org:act: 97E8B9CE-D4B3-40CE-B308-736C8B330F6E Holotype: LMA-00318, L: 0.33 mm, H: 0.21 mm, W: 0.17 mm. Material: One carapace and one valve. Derivation of name: Refers to its reticulate ornamentation like the geometry of the honeycombs produced by bees. Type locality: Crato Formation, Araripe Basin, Nova Olinda Municipality, Ceará State, Brazil. Type horizon: Crato Formation, Santana Group, Araripe Basin, Brazil. 2-AR-SR-1A-CE well core sample, depth interval 120.39–120.42 m. Outcrop sample 1BAr17b (Três Irmãos Quarry). Stratigraphic and geographic distribution: Aptian:Crato Formation,Araripe Basin, Nova Olinda Municipality, Ceará State, Brazil (Guzmán et al. 2022, 2023; this study). Diagnosis: A Theriosynoecum species with sub-rectangular outline in lateral view, dorsal margin straight, sloping to the posterior region. Cardinal angles well defined, especially the posterior one. Surface reticulate. Description: Carapace sub-rectangular in lateral view; fusiform in dorsal view. Ventral margin straight, but its outline in lateral view is slightly convex; dorsal margin straight, sloping to the posterior region; anterior margin broadly rounded; posterior margin straight to weakly rounded at posteroventral position. Two sulci are present from the dorsal region to mid-height, the first one at the anterior third and the second one just behind mid-length position. LV overlapping RV, subtly at the region of the posterior cardinal angle and at posteroventral region. Maximum height at the anterior cardinal angle; greater length at mid-height; greater median width. Obtuse cardinal angles. Carapace surface ornamented with wide reticula, exhibiting shallow sub-hexagonal fossae, narrow muri showing a few intramural pore canals and sola punctuated more perceptible on the left valve. Sexual dimorphism and internal features not observed. Remarks: Theriosynoecum favus sp. nov. stands out due to the small size of its carapace, which could indicate that it is a juvenile. However, the possibility that this is an instar of an already described species is excluded, when compared to Theriosynoecum silvai (Silva, 1978) emend. Do Carmo et al., 2013, the only post-rift species with a known complete ontogenetic series, which displays the ventral region ornamented by subparallel rows, an asymmetrically rounded anterior margin and a very marked anterior cardinal angle, features that are not observed in Theriosynoecum favus sp. nov. The valve recovered was fragmented during the imaging process, making it impossible to observe its internal characters to compose the description and diagnosis of this species and the designation of a paratype.