Pseudogryllotalpidae, Cadena-Castañeda, Oscar J., Tavares, Gustavo Costa, Hu, Tian-Hao & He, Zhu-Qing, 2024

Cadena-Castañeda, Oscar J., Tavares, Gustavo Costa, Hu, Tian-Hao & He, Zhu-Qing, 2024, On the Myanmar amber field-crickets described as “ transitional ” mole crickets (Orthoptera: Gryllidea), Zootaxa 5555 (4), pp. 579-589 : 582-584

† Pseudogryllotalpidae Gu, Yuan & Ma, 2024 syn. nov.

Comments. †Pseudogryllotalpidae syn. nov. is proposed as a synonym under † Pherodactylina for the following reasons:

According to the principle of priority, † Pherodactylina is the oldest name that groups the fossil taxa † Pherodactylus (type genus) and † Burmagryllotalpa, sensu Cadena-Castañeda et al. (2023) . Gu et al. (2024) later included these two genera in †Pseudogryllotalpidae syn. nov., along with additional genera such as † Pseudogryllotalpa (type genus), † Unidigitus, and † Petilus, as well as genera synonymized by Cadena-Castañeda et al. (2023) like † Tresdigitus . †Pseudogryllotalpidae syn. nov. was conceptualized similarly to † Pherodactylina , so we propose them as synonyms.

Regarding morphology, †Pseudogryllotalpidae syn. nov. is diagnosed as having “Proximal flagellomeres markedly compressed; prothoracic legs robust, protibia paddle-like with dactylar processes on the inner side; probasitarsus elongated; mesotibia with two parallel rows of long dorsal setae; metatibia strong, covered by dense and stout setae, with some small denticle-like spines on the inner dorsal margin, becoming larger apically” ( Gu et al. 2024). However, some discrepancies arise if we examine each characteristic:

1) “Proximal flagellomeres markedly compressed.” When comparing this with the specimens studied by Cadena-Castañeda et al. (2023) and the photographs and drawings by Gu et al. (2024), this character is not as evident as described by Gu et al. (2024). At least, the flagellomeres have a similar shape, tending to be sub-cylindrical. However, the scape may be moderately flattened dorsoventrally (although not very prominent), as seen in various field crickets like Sclerogryllus Gorochov, 1985 or Mellogryllus Cadena-Castañeda, Tavares & Fernandes, 2022 ( Gryllinae ), and even in Majialandrevus He, 2021 and different Odontogryllini genera ( Landrevinae ) ( Cadena-Castañeda et al. 2022, 2023; Campos & de Mello 2014; Oya et al. 2024), among others. This demonstrates it is not an exclusive characteristic of †Pseudogryllotalpidae syn. nov., even though it is one of the two homologous characters (character 9: state 1) supporting this taxon. Upon examining this character and realizing it is not exclusive to †Pseudogryllotalpidae syn. nov., the clade grouping this family would lose stability.

2) “Prothoracic legs robust, protibia paddle-like with dactylar processes on the inner side.” This characteristic was analyzed by Cadena-Castañeda et al. (2023). The comparison shows the different modifications seen in groups of orthopterans with legs adapted for digging. Although different, these groups share a pattern where the apical spurs of the fore tibiae take the form of dactyls or thickened spurs. Since they exhibit fossorial behavior, the effort required for digging is reflected in the first pair of legs being more robust than usual compared to related groups. That occurs in mole crickets, Jerusalem crickets, sandgropers, pygmy mole crickets, and modern field crickets, which are the most notable examples. That demonstrates that modifying the first pair of legs for digging has appeared multiple times and could be considered a convergence of different groups of orthopterans that share a subterranean lifestyle.

This characteristic was codified in the morphological matrix used by Gu et al. (2024) and corresponds to the binary character16 (leg development). Some comments must be made regarding the codification of this character once the two states are (0) “Not Sturdy” and (1) “Sturdy.” Additionally, this character was recovered as a synapomorphy of the clade Gryllotalpoidea + †Pseudogryllotalpidae. However, this character seems arbitrary, as no parameters define what constitutes a robust foreleg. All representatives of †Pseudogryllotalpidae were coded as having robust legs (state 1, see Gu et al. 2024, Data S2). However, these crickets have legs similar to modern burrowing crickets, such as Mellogryllus . Additionally, the species Myrmecophilus americanus Saussure ( Myrmecophilidae ) was also coded as state 1, meaning it has a robust leg. However, these crickets have slender legs because, despite living in cavities, they are not burrowers but rather parasites in ant nests. Thus, they do not dig galleries; they merely take advantage of those built by ants ( Junker, 1997).

3) “Probasitarsus elongated.” This characteristic could be subject to variation. For example, it is not specified how elongated it is, which can lead to subjective interpretation. The consistent feature of this characteristic in the different fossil taxa analyzed here is that the first tarsomere of the foreleg can be as long as one-third or half the length of the foretibia. However, this first tarsomere can be similar in size to the third tarsomere or slightly longer, as can happen in different groups of crickets like Gryllidae or some Phalangopsidae , among others ( Desutter 1990; Cadena-Castañeda & García García 2020; Tavares et al. 2024).

A similar character was used in the phylogenetic matrix and coded as the multistate character 23 (Probasitarsus length), with the state (0) “Basitarsus equal to the third tarsomere,” (1) “Basitarsus longer than the third tarsomere,” and (2) “Basitarsus shorter than the third tarsomere.” All †Pseudogryllotalpidae syn. nov. species (with available information) were coded as state 1. However, this clearly is not a unique characteristic of this taxon once other Grylloidea terminal taxa were also coded as state 1 (see Gu et al. 2024, Data S2).

4) “Mesotibia with two parallel rows of long dorsal setae.” This character is one of the synapomorphies (character 27: state 1) that supports the clade of †Pseudogryllotalpidae syn. nov. This has not been formally documented in other field crickets. However, it is also observed in other ground crickets such as Mellogryllus , Zebragryllus , and Xulavuna de Mello & Campos, 2014 ( Cadena-Castañeda, Tavares & Fernandes 2022; Oya et al. 2024; Tavares et al. 2024). It suggests that this characteristic may occur in other crickets but has not been recorded in descriptions or studies, so it has probably been overlooked.

5) “Metatibia strong, covered by dense and stout setae and with some small denticle-like spines on the inner dorsal margin, becoming larger apically.” This character is observed in modern and fossil Sclerogryllini ( Cadena-Castañeda et al. 2023) . This characteristic should also be evaluated in different groups of orthopterans with fossorial habits to confirm in which groups it might be present.

In addition to the characteristics presented in the diagnosis, we have to discuss some characters coded in the phylogenetic matrix and recovered as synapomorphies of Grylloidea and Gryllotalpoidea + †Pseudogryllotalpidae. Regarding Grylloidea , three characters were recovered as synapomorphies: 29(0), 34(0), and 37(0). The homologous state 0 (no) of character 29 (Mesotibia with apical spurs ia1, ia2, oa1, and oa2) was recovered as a synapomorphy of Grylloidea . All terminals of the clade Gryllotalpoidea + †Pseudogryllotalpidae and the two outgroups were coded as state 1 (yes). However, it is not possible to visualize the ventral apical spur in any of the presented images of the †Pseudogryllotalpidae specimens, only in the vector illustrations where a small ventral spur is represented behind the other spurs (see Gu et al. 2024, Figs 4D, 5F). In the original description of Pherodactylus micromorphus , the authors described it as having only four median spurs ( Poinar et al. 2020). Modern gryllotalpids also have four apical spurs on the mesotibia, as does Marchandia magnifica Perrichot, Néraudeau, Azar, Menier & Nel (2002) . However, all these taxa were coded as having five spurs. It was not possible to confirm if the outgroups, Aboilomimus ornatus Liu, Zhou, Bi & Tang and Mecopoda niponensis (Haan) , had four or five apical spurs once this character is not described in the original descriptions. However, it is not of our knowledge that any Tettigoniidae has five apical spurs.

The homoplastic state 0 (no) of character 34 (Metatibia apical spurs disposed around the tibial apex) was recovered as a synapomorphy of Grylloidea . However, the apical spurs of all taxa of †Pseudogryllotalpidae syn. nov., represented in all the images presented in the work of Gu et al. (2024) or of previously described species ( Cadena-Castañeda et al. 2023; Poinar et al. 2020), are arranged in pairs, three on each margin, as in other Grylloidea .

Regarding the clade Gryllotalpoidea + †Pseudogryllotalpidae, the homologous state 1 (longer than the pronotum but shorter than the body) of character 7 (antenna length) was recovered as a synapomorphy. However, this trait is frequently found in Gryllidae , especially those with burrowing habits (e.g., Zebragryllus and Mellogryllus ) ( Oya et al. 2024; Tavares et al. 2024). The species Myrmecophilus (Myrmophilina) americanus Saussure, 1877 (Myrmecophylidae) was also coded as state 1, meaning its antennae are longer than the pronotum but shorter than the body. However, these crickets have antennae that are slightly longer than their bodies.

The homologous state 1 (with strong setae) of character 20 (external surface of the fore tibia) was recovered as a synapomorphy of Gryllotalpoidea + †Pseudogryllotalpidae. However, this trait is also found in Mellogryllus . The species M. americanus (Myrmecophylidae) was also coded as state 1, meaning it possesses such setae on the fore tibia. However, Myrmecophilus species do not exhibit this trait.

The homoplasious state 1 (yes) of character 25 (ventral surface of the probasitarsus with strong setae) was recovered as a synapomorphy (homoplasy) of Gryllotalpoidea + †Pseudogryllotalpidae. However, this trait is also found in Mellogryllus .

The homologous state 1 (yes) of character 31 (metatibia gradually thickened from the base to the tip) was recovered as a synapomorphy of Gryllotalpoidea + †Pseudogryllotalpidae. However, there is clear subjectivity here, as all representatives of Gryllotalpoidea and †Pseudogryllotalpidae syn. nov. were coded as having this character, but the metatibia presented in the work resembles that of a common modern cricket, with a slight gradual thickening from the base to the apex. Additionally, Myrmecophilus species have the metatibia slightly enlarged medially but narrow apically. On the other hand, the terminals used in the matrix to represent Grylloidea were coded as not having such a character state.

Finally, it became clear to us that the codification of the matrix characters left room for subjectivity.Additionally, when analyzing the diagnostic characteristics of †Pseudogryllotalpidae syn. nov., it becomes clear that they are not entirely exclusive to this family. However, compared with the morphological analysis of Cadena-Castañeda et al. (2023), it is evident that †Pseudogryllotalpidae syn. nov. is a synonym of † Pherodactylina . Based on the same arguments provided in that morphological analysis, the original placement of † Pherodactylina as a subtribe of Sclerogryllini is preserved, dismissing the idea that it represents a different family or a transitional group between crickets and mole crickets. On the contrary, these fossil crickets and the recently described M. mutus are notable examples of morphological convergence due to a similar lifestyle.