(Figure 14B)
Uca thayeri Rathbun, 1900: 134.
Material examined. Brazil, São Paulo: 1 ♂, CCDB 2540, Ubatuba, river near Praia Perequê-Açu, colls. F. Mantelatto & C. Tudge, 25.xi.2008; 2 ♂, CCDB 2364, Ubatuba, Rio Escuro mangrove, colls. F. Mantelatto et al., 03.vi.2008; 1 ♂, CCDB 2992, Ubatuba, Rio Escuro mangrove, coll. F. Mantelatto, 15.v.2010; 1 ♂, CCDB 1930, Ubatuba, Rio Escuro mangrove, colls. F. Mantelatto et al., 05.iv.2011; 3 ♂, CCDB 4034, Ubatuba, Rio Escuro mangrove, colls. R. Buranelli et al., 23.iv.2012; 1 ♂, CCDB 2987, Cananéia, Ponte General Euclides de O. Figueiredo, colls. F. Mantelatto et al., 13.v.2008; 1 ♂, CCDB 4027, Ilha Comprida, beach near ferry station to Cananéia, colls. F. Carvalho et al., 09.xi.2011; 1 ♂, CCDB 784, Cananéia, estuary, colls. R. Costa et al., 30.viii.2011; 5 ♂, CCDB 798, Cananéia, estuary, colls. R. Costa et al., 30.viii.2011; 1 ♂, CCDB 3220, Cananéia, Rio Bragança estuary, colls. R. Costa et al., 17.iv.2011.
Distribution. Western Atlantic—USA (Florida), Gulf of Mexico, Cuba, Jamaica, Puerto Rico, Guatemala, Trinidad and Tobago, Venezuela, and Brazil (Pará, Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia, Espírito Santo, Rio de Janeiro, São Paulo, Paraná, Santa Catarina) (Rathbun 1918; Chace & Hobbs 1969; Crane 1975; Bezerra 2012; Masunari et al. 2020).
Remarks. Previous records on the coast of São Paulo include Cananéia (Gerlach 1958), Ubatuba, and Cubatão (Bezerra 2012). According to Masunari et al. (2020), the occurrence in Piauí is probable but not officially recorded and this species is easily confused with other species of Brazilian fiddler crabs, due a very narrow triangular front. Sequences accession number (GenBank): CCDB 1930—16S (KU313150), COI (KU313431) (Mantelatto et al. 2018a).