Mexico stands out as having one of the greatest biodiversity in the world, including animal radiation, being, among other things, a center of diversity for Diplopoda, scorpions, reptiles. Here we list the highlights of Mexican metazoan diversity in relation to Brazilian diversity, based on the Synopsis of Brazilian Animal Diversity text.
▪ Keys to Nearctic Fauna (BOOK), edited by James H. Thorp and D. Christopher Rogers, published in 2016, as KNF/2016.
▪ Keys to Neotropical and Antarctic Fauna (BOOK), edited by Cristina Damborenea, D. Christopher Rogers and James H. Thorp, published in 2020, as KNAF/2020.
Orthonectida, Micrognathozoa and Cycliophora are absents in Mexico and Brazil. Gnathostomulida has no species described in either Mexico or Brazil, but it certainly has to be described, due to the abundance of these animals throughout the world's oceans.
No data for Mexican marine Porifera non Desmopongieae, Cnidaria/Anthozoa, Acoela, Gastrotricha, Platyhelminthes, Nemertea, Bryozoa, Entoprocta, Brachiopoda, Priapulida, Branchiopoda, Maxillopoda, Malacostraca non Decapoda, Hemichordata and Tunicata.
Xenoturbellida, Dicyemida, Asymmetron, Remipedia, Monoplacophora and Petromyzontii are canonic lineages in Mexico absents in Brazil.
Mexico includes 33 Ctenophora (SEE), and only 13 in Brazil.
PORIFERA
Mexico includes 517 spp. of Demospongiae (SEE), Brazil only 373. No data for other groups.
In cave fauna Brazil has two spp., and Mexico only one, undescribed.
PLACOZOA
Brazil and Mexico has the same species.
CNIDARIA
8 clades, same 7 in Mexico and Brazil. These 7, Brazil leads in four: Cubozoa (3 ✕ 5 Brazil), Scyphozoa (20 ✕ 22 Brazil), Hydrozoa (266 ✕ 348 Brazil) and Myxozoa (47 ✕ 111 Brazil, SEE). No data for Hexacorallia, Octocorallia and Staurozoa.
The most notable taxon is the unbrazilian family Botrucnidiferidae (Botruanthus benedeni) from Galapagos, also in California and Baja California.
XENOCOELOMORPHA
Six worms belongs the single genus Xenoturbella (Wikipedia): four from coasts of California (1) and Gulf of California (3, NW Mexico) in Pacific Ocean (Rouse et al., Nature, 2016), one from coast of Japan (Nakano et al., BMC Evol Biol., 2017), and, by same reference, the type species, from waters of Sweden. Absent in Brazil. No relevant unbrazilian Mexican taxon in remaining groups.
CHAETOGNATHA
Mentions of (2/)12 spp. in Baja California (SEE), (7/)14 in W portion of Gulf of Mexico on Mexican EEZ (SEE) and (7/)12 in Campeche bank (SEE). All species from Campeche Bank occur in W Gulf Mexico except Pterosagitta draco. Overall, (7/)14-27 sp. in Mexico, and 25 in Brazil.
GNATHOSTOMULIDA
Oficially a phyllum absent in both countries. However, two undescribed species was collected in SE Brazil.
MICROGNATHOZOA
A phyllum absent in both countries.
SYNDERMATA
Three clades, with Seison absent in both Mexico and Brazil. Brazil leads in both remaining clades: Eurotatoria (Brazil 625 ✕ 402 Mexico/SEE) and Acanthocephala (Brazil 72 ✕ 60 Mexico/SEE).
ORTHONECTIDA
Absent in Mexico and Brazil.
DYCIEMIDA
112 spp. within three families and nine genera (Conocyemidae, Dicyemidae and Kantharellidae, Wiki), two in Mexico, Dicyemina shorti (Veracruz) and Dyciema guaycurense (Baja California Sur). Brazil not has this phyllum.
GASTROTRICHA
No consistent data for Mexico.
PLATYHELMINTHES
No data for Mexico.
ENTOPROCTA
No data for Mexico.
CYCLIOPHORA
Absent in Brazil and Mexico.
NEMERTEA
No data for Mexico.
ANNELIDA
Former Polychaetes was merged with Echiura and Sipuncula, and split in 18 lineages. Mexico includes (63:460/)1,500 spp. of former Polychaetes (Tovar-Hernández, Revista Mexicana de Biodiversidad, 2014), and Brazil has only 1,149.
The highest record of a freshwater non-Clitellate Annelida in world belongs Lycastoides alticola from Mexico, found at 2,150 m a.s.l. in Mexico (Conde-Vela, Subterranean Biology, 2017). Clitellate families Randiellida, Phreodrilidae, Lumbricidae and Sparganophilidae possibly occur in Mexico.
In Mexico also occur (6/)17 spp. of Branchiobdellida (one of 15 Clitellata orders, obligate ectosymbionts primarily associated with astacoidean crayfishes): Bdellodrilus (1), Cambarincola (9), Pterodrilus (1), Forbesodrilus (2, Mexico and Nicaragua), Oedipodrilus (1) and Sathodrilus (3), at Thorp & Rogers (BOOK, 2017).
BRACHYOPODA
Three clades. Mexico includes 11 genera absents in Brazil, 8 of them in Rhynchonelliformea.
Linguliformea (SEE) ‣ six living genera in a single order, Glottidia (MAP) and Pelagodiscus (MAP) absents in Brazil and presents in Mexico.
Rhynchonelliformea (SEE) ‣ three orders.
Order Rhynchonellida ‣ a group absent in Brazil, two genera in Mexico: Cryptopora (MAP) and Neorhynchia (MAP), one also in South America.
Order Thecideida ‣ a group absent in Brazil, two genera in Mexico: Lacazella (MAP) and Minutella (MAP).
Order Terebratullida ‣ Mexican genera absents in Brazil: Liothyrella (MAP), Abyssothyris (MAP), Terebratullina (MAP) and Macandrevia (MAP).
Craniiformea (SEE) ‣ two Novocrania occur in Mexico (Robinson, Zootaxa, 2017), group absent in Brazil.
BRYOZOA
No data for Mexico.
PHORONIDA
5 spp. in Brazil, 3 in Mexico. Mexico includes Phoronis ijimae (SEE), a Brazilian outsider, in extreme NW Pcific coast.
LORICIFERA
Six specimens were found in southern Gulf of Mexico, including representatives of new species of Pliciloricus and Rugiloricus, an undescribed genus of Pliciloricidae and, possibly, an undescribed genus of Nanaloricidae (SEE). Only one sp. in Brazil.
KYNORRHYNCHA
24 spp. in Mexico, 3 in Echonoderes (SEE), and only 8 in Brazil.
PRIAPULIDA
Only one sp. in both countries. Mexican species is a Priapulus (SEE).
NEMATOMORPHA
Gordionus, the unique South American genus absent in Brazil, not occur in Mexico (KNAF/2020; KNF/2016).
NEMATODA
No data for both countries.
TARDIGRADA
Brazil includes 100 spp., Mexico only 55 (SEE).
ONYCHOPHORA
Brazil includes 29 spp., Mexico only three: Macroperipatus perrieri from Veracruz, Oroperipatus eisenii from Nayarit and an undescribed species of Oroperipatus from Tuxtla Gutiérrez, Chiapas (SEE).
HEMICHORDATA
Rhabdopleurida, the unique Brazilian outsider order, does also not occur in Mexico (MAP).
ECHINODERMATA
Currently, 643 spp. are known from Mexico, in Ophiuroidea (197 ✕ 153 Brazil), Asteroidea (185 ✕ 77 Brazil), Echinoidea (119 ✕ 52 Brazil), Holothuroidea (113 ✕ 49 Brazil) and Crinoidea (29 ✕ 16 Brazil), by Solís-Marín et al. (Echinoderm Research and Diversity in Latin America, 2012).
CEPHALOCHORDATA
Both Brazil and Mexico has 3 Branchiostoma. However, Mexico also includes Asymmetron lucayanum, in front of the northeastern coast of Yucatan.
TUNICATA
No data for Mexico.