Pheidole cordata (Holl, 1829)

Boudinot, Brendon E., Bock, Bernhard L., Weingardt, Michael, Troeger, Daniel, Batelka, Jan, LI, Di, Richter, Adrian, Pohl, Hans, Moosdorf, Olivia T. D., Jandausch, Kenny, Hammel, Joerg U. & Beutel, Rolf G., 2024, Et latet et lucet: Discoveries from the Phyletisches Museum amber and copal collection in Jena, Germany, Deutsche Entomologische Zeitschrift 71 (1), pp. 111-176 : 111

‡ Pheidole cordata (Holl, 1829)

Figs 19 , 20 , 21 : Fig. A5

Neotype.

PMJ Pa 5889, designated here. Figs 19A-D , 20A-D , 21B, D, F .

Locality and horizon.

East African copal (IAA results for PMJ Pa 5889: copal (Table 1 ); 14C-dating for PMJ Pa 5889: ~700 years old).

Syninclusions.

Platygastridae , Ceratopogonidae , and Lepidoptera .

Preservation.

The cuticle is preserved as a distinct layer as seen in the SR-µ-CT scan data. Most of the soft tissues are absent, except for parts of the digestive tract and some musculature, such as parts of the mandibular adductor (0 md1) and some muscles of the legs. The endoskeleton of the head and mesosoma is distinctly preserved and can be meaningfully used for future comparative anatomy.

Paraneotypes.

None.

Diagnosis.

The species, represented by the major worker, is identifiable as a member of the Ph. megacephala species group by (1) the presence of the conspicuous ventral convexity of the postpetiolar sternum (Fig. 19A; e .g., Salata and Fisher 2020). It differs from Ph. megacephala (Fabricius, 1793), Ph. megatron Fischer & Fischer, 2013, and Ph. spinosa Forel, 1891 by (2) the well-developed inner hypostomal teeth (Fig. 20B; e .g., Salata and Fisher 2022). Among the Pheidole megacephala group species more broadly (e.g., Fischer et al. 2012), it differs in having (3) facial rugosity that extends to the posterior margin of the occipital lobes (Fig. 20A , note: among type specimens of the group imaged on AntWeb, this condition also occurring in Ph. megacephala impressifrons Wasmann, 1905, which has a more angular bulge of the postpetiolar sternum). See the description below for further conditions.

Description.

Measurements (in mm; abbreviations follow Salata and Fisher 2022): EL = 0.152; HL = 1.290; HW = 1.230; MTL = 0.673; PNW = 0.618; PPW = 0.324; PSL = 0.202; PTW = 0.172; SL = 0.714; WL = 1.110.

Indices (also following Salata and Fisher 2022): CI = 95.3; MTI = 54.7; SI = 58.0; PNI = 50.2; PPI = 26.3; PSLI = 16.4. Note: Measurements taken from cross-sectional projections in DragonFly using the reregistration and ruler tools.

Head. In full-face view (Figs 19B , 20A ), the head is subcordate, with the lateral margins widest somewhat beyond head midlength and with the posterior portions of the lateral margins converging posterad to the occipital lobes. In lateral view (Fig. 19A ), the head is subovate. The antennal scrobes are indistinct. The occipital lobes are rugose, with shagreened interspaces. The inner hypostomal teeth are well-developed; they are distant from the outer teeth, which are also well-developed (Fig. 20B ). The median hypostomal tooth is indistinct.

Mesosoma. The humeral tubercle of the pronotum is weakly developed. The mesonotal bulge is distinct but not pronounced. The metanotum is only weakly indicated by a slight angularity of the promesonotal profile in lateral view. The propodeal spines are moderately long, with a wide base and acute tip (Fig. 19A ).

Metasoma. The bulge of the postpetiolar sternum is rounded anteriorly. The first gastral tergum (ATIV) appears to be shagreened at its base (Fig. 20D ).

Setation. Length and stature of setation uncertain, although density measurable in the scans based on the distinct occurrence of the setiferous punctation.

Coloration. Not clearly visible; appears brownish/reddish.

Remarks on the neotype.

Designation of the soldier in piece PMJ Pa 5889 as the neotype of ‡ Ph. cordata meets the requirements of article 75 of the ICZN (1999), as follows. 75.3.1. The identity of this taxon is in severe need of clarification, as it has vexed systematists for nearly two centuries (e.g., Mayr 1868; Casadei-Ferreira et al. 2019) and may mistakenly be used for evolutionary inference, such as an Eocene-aged calibration for divergence dating based on the assumption that it is from Baltic amber, as recorded by, e.g., Bolton (1995, p. 319) and Bolton (2003). 75.3.2, -.3. Diagnostic remarks and description are provided above. 75.3.4. The original material is known to be lost ( Casadei-Ferreira et al. 2019). It is unclear if the material sent by Schweigger ever made it to the MfN Berlin in the first half of the 19th century; see p. 111 of Schweigger (1819) and elsewhere for his stated intent to have the specimens identified there. Further, Holl (1829, p. 140) indicates that he defined his species † Formica cordata based on the observations of Schweigger and Mayr (1868, p. 18) explicitly states that he had not seen the material referred to by Holl. 75.3.5. The neotype matches the best available evidence. More specifically, the first author of the present work directly examined a physical print of the original illustrations by Schweigger (1819, figs 70, 70a, 70b on plate 8 therein; Fig. 21A, C, E ), which were used by Holl (1829) to designate the species. Based on this, that author observed clearly illustrated 3-merous antennal clubs, which would rule out other Afrotropical Myrmicinae ( Fisher and Bolton 2016). The illustrations further show attributes of Pheidole , including a massive head, high and domed promesonotum, low and spined propodeum, and long petiolar peduncle with a short node. Mayr (1868) was uncertain about the size of the original material, which is unknowable at this point and irrelevant for the present designation. Therefore, we interpret the fossil as Pheidole based on the available evidence (Fig. 21B, D, F ), which is restricted to the examined copper plate due to loss of the original material. 75.3.6. The designated neotype does come from the original type locality and horizon as much as is practicable, given that Schweigger (1819): (a) knew about copal (pp. 103, 104 therein) and East African copal was available around that time (e.g., Smith 1868, see section 4.3.2 below); (b) he was uncertain about the provenance of the two specimens eventually named ‡ Ph. cordata by Holl (1829), as stated in the text; and (c) he pointed out that the species he examined resembled a taxon possibly from Africa ("Diese Bildung findet sich an Ameisen südlicher Länder.”, pp. 119 therein). Regarding the type locality further, although we cannot be absolutely certain that the specific fossil is from East African or Malagasy copal sensu lato, the syninclusion of a Pheidole minor from the PMJ Pa collection with Dorylus (PMJ Pa 5827), which has never been recorded from Madagascar, strongly implies that the material was from the mainland of the African continent. 75.3.7. The neotype is permanently preserved in and available for study at the Phyletisches Museum, Jena.

We have taken this action to resolve a suite of problems associated with the name ‡ Ph. cordata , as recently reviewed by Casadei-Ferreira et al. (2019), who, after much consideration, concluded by placing this fossil incertae sedis in Myrmicinae . We fully agree with Casadei-Ferreira et al. (2019) that this fossil needs to be disposed of in order to avoid its uncritical use in systematic or evolutionary study and inference. By placing the name ‡ Ph. cordata back in Pheidole , we alleviate the need for treating this taxon in the next revision of the fossil record of Myrmicinae , particularly as the specific epithet will be paired with the genus Pheidole , unless it were returned to Formica , to which it certainly cannot belong. Further, by designating a neotype we permanently fix this name to a known specimen that is both preserved in perpetuity in the PMJ Pa collection and is available for global evaluation via the cybertype data. Finally, there is no possibility beyond egregious error for this taxon to be used as an Eocene calibration for Pheidole as the neotype is from 14C-dated copal. (copal sensu lato).

Remarks on Afrotropical Pheidole .

It is widely appreciated among myrmecologists working on Pheidole that the genus is in severe need of revision both globally and in the Afrotropical region ( Wilson 2003; Fischer et al. 2012; Sarnat et al. 2015), which is also the particular case for the Pheidole megacephala species group ( Fischer et al. 2012; Salata and Fisher 2022). While we would strongly prefer to not provide a one-off description of a Pheidole due to this complicated problem, we accept this as necessary and acceptable only in order to resolve the problem of ‡ Ph. cordata , which is otherwise an irksome thorn-in-the-side bestowed upon generations of us by the well-meaning cataloging work of Holl (1829).

Although ‡ Ph. cordata as typified here cannot be included in barcoding or phylogenomic datasets given its poor soft tissue preservation, it is our hope that the SR-µ-CT data may allow the confident and quantitative placement of this species among the species allied to Ph. megacephala via a dedicated revision of this species group. As noted in our diagnosis above, the neotype of ‡ Ph. cordata (PMJ Pa 5889) is most similar to Ph. megacephala impressifrons , being most starkly distinguished from this form by the form of the postpetiolar sternum in lateral view. Notably, the form of the medial hypostomal teeth has not been recorded for the various forms of Ph. megacephala and similar species (e.g., Fischer et al. 2012). Whether the newly typified species ‡ Ph. cordata is extant is an open question; it is plausible that the historical habitat has been destroyed, hence this species may be considered a candidate Lazarus taxon. Further exploration of known Afrotropical copal sensu lato and extant myrmecofauna will be of considerable value.

3.3.3. Order Neuroptera : Synopsis of Nevrorthidae

3.3.3.1. Family Nevrorthidae Nakahara, 1915. [Note 1]

I. Genus † Balticoneurorthus Wichard, 2016.

A. Baltic ambers [Eocene, 37.8-33.9 Mya].

1. † Ba. elegans Wichard, 2016. [m].

II. Genus † Cretarhopalis Wichard, 2017.

B. Kachin amber [Myanmar; Cretaceous, 99.6-93.5 Mya].

1. † Crh. patrickmuelleri Wichard, 2017. [f].

III. Genus † Electroneurorthrus Wichard, Buder & Caruso, 2010.

A. Baltic ambers [see above].

1. † El. malickyi Wichard, Buder & Caruso, 2010. [f].

IV. Genus † Girafficervix Du, Niu & Bao, 2023.

C. Daohugou shale [China; Jurassic, 166.1-157.3 Mya].

1. † G. baii (Du, Niu & Bao, 2023). [l].

V. Genus † Palaeoneurorthus Wichard, 2009.

A. Baltic ambers [see above].

1. † Pa. bifurcatus Wichard, 2009. [m].

2. † Pa. eocaenus Wichard, 2016. [m].

3. † Pa. groehni Wichard, Buder & Caruso, 2010. [m].

4. † Pa. hoffeinsorum Wichard, 2009. [m]. [Type species!].

VI. Genus † Proberotha Krüger, 1923.

A. Baltic ambers [see above].

1. † Pr. dichotoma Wichard, 2016. [f].

2. † Pr. eocaenus Krüger, 1923. [m, f]. [Type species!].

VII. Genus † Rhopalis Pictet, 1854.

A. Baltic ambers [see above].

1. † Rh. relicta Pictet, 1854. [f, m]. (See also: Wichard et al. 2010.)

VIII. Genus † Sisyroneurorthus Nakamine, Yamamoto, Takahashi & Liu, 2023.

B. Kachin amber [see above].

1. † S. aspoeckorum Nakamine et al., 2023. [f].

Note 1. Six of the eight fossil genera of Nevrorthidae are monotypic. For those two genera that have more than one species attributed to them, the type species is indicated.

3.3.3.2. Genus Palaeoneurorthus Wichard, 2009

Figures

Figure 19. A-D. 3 D-reconstruction of the neotype of ‡ Pheidole cordata A. Habitus in lateral view; B. Habitus in frontal view; C. Habitus in dorsal view; D. Habitus in ventral view. Abbreviation: ppd = propodeum.

Figure 20. A-D. 3 D-reconstruction of the neotype of ‡ Pheidole cordata preserved in piece PMJ Pa 5889. A. Details of head in frontal view, arrow indicates occipital lobe; B. Detail of mouthparts in ventral view; C. Details of foreleg in lateral view; D. Details of metasoma in dorsolateral view. Abbreviations: IHT = inner hypostomal tooth, OHT = outer hypostomal tooth.

Figure 21. A, C, E. Copper lithographs by Schweigger (1819), which Holl (1829) named † Formica cordata. B, D, F. Photographs of the neotype of ‡ Pheidole cordata A. Overview of the amber piece; B. Overview of the amber piece, arrow indicates the inclusion; C. Habitus in lateral view; D. Habitus in ventrolateral view; E. Habitus in dorsal view; F. Habitus in dorsolateral view.

Figure A 5. Model 5 of the neotype of ‡ Pheidole cordata Holl, 1829 preserved in copal piece PMJ Pa 5889. An interactive cybertype is available in the HTML version of this article online and on Sketchfab: URL: https: // sketchfab. com / 3 d-models / pheidole-cordata- 695385 c 99247469 ebb 28 bc 4049 b 9 e 301.