Sciency Thoughts: Mexican Amber

Showing posts with label Mexican Amber. Show all posts

Friday, 1 November 2024

Pheidole praehistorica: A new species of Spiny Ant from Oligo–Miocene Chiapas Amber.

The genus Pheidole is currently considered to be the most diverse genus of Ants, with 1160 living and six fossil species. Although global in distribution, the genus is at its most diverse in the Neotropics, and is presumed to have originated in this region. This is supported by the locations from which the known fossils in the genus have been recovered, with the oldest known species coming from the Eocene of Colorado, and other fossils known from the Miocene of the Dominican Republic (three species), and the Oligo-Miocene of Chiapas State, Mexico (2 species).

In a paper published in the European Journal of Taxonomy on 25 October 2024, Fernando Varela-Hernández & Franciso Riquelme of the Laboratorio de Sistemática Molecular at the Universidad Autónoma del Estado de Morelos, describe a third species of Pheidole from Chiapas Amber.

Chiapas Amber comes from the Simojovel, Totolapa, and Estrella de Belén localities in the Chiapas Highlands of southern Mexico, with the Simojovel site being the main centre of commercial amber extraction. The amber comes from a series of limestone, sandstone, siltstone, shale, and lignite beds of Late Oligocene to Early Miocene age, referred to as either the Simojovel Formation or the La Quinta Formation. The amber here is thought to have derived from a type of Leguminous tree of the genus Hymenaea; resin-producing trees belonging to this genus are also thought to have been responsible for Dominican Amber, which is of approximately the same age as Chiapas Amber, and are still found today across the Neotropics.

The new species is named Pheidole praehistorica, where 'praehistorica' means 'prehistoric' in reference to the nature of the material from which it is described, five fossil Ants trapped within a single species of amber.

Pheidole praehistorica. (A)–(C) Holotype (CPAL.464). (A) Profile view. (B) Frontal view. (C) Closer lateral view of the head and mesosoma. (D) Paratype (CPAL.465), latero-frontal view of the head. (E) Paratype (CPAL.468), profile view. Abbreviations: acl, antennal club; an, antenna; cly, clypeus; ey, eyes; fl, foreleg; ga, gaster; ha, hairs on clypeus; hd, head; hl, hind leg; mn, mandible; nck, neck; p, petiole; pn, pronotum; pns, pronotal spine; pp, postpetiole; pps, propodeal spine; sc, scape. Varela-Hernández & Riquelme (2024).

Pheidole praehistorica is smaller than other species from Chiapas Amber, an average length of 2.3 mm, and has shorter pronotal spines (spines on the forward part of the thorax, immediately behind the head) and straight propodeal spines (spines on the rear part of the thorax, immediately before the abdomen.

Saturday, 13 April 2024

A hitchhiking Pseudoscorpion from Chiapas Amber.

Phoresis is an interaction in which an Animal hitches a ride on another Animal purely for the purpose of transport. This is found in a variety of Animal groups, but is particularly common in Mites and Pseudoscorpions. Unusually for an Animal behaviour, phoresis has a fairly long fossil record, with the oldest known example being a Mite found attached to an early Orthopteran Insect from from the Carboniferous Tupo Formation of China, and the oldest known example involving a Pseudoscorpion coming from Cretaceous Burmese Amber.

In a paper published in the journal Historical Biology on 7 April 2024, Víctor Córdova-Tabares of the Universidad Autónoma del Estado de Morelos and the Departamento de Zoología at the Escuela Nacional de Ciencias Biológicas, Francisco Riquelme, also of the Universidad Autónoma del Estado de Morelos, and Gabriel Villegas-Guzmán, Javier Víctor, and Emilio Estrada Ruiz, also of the Departamento de Zoología at the Escuela Nacional de Ciencias Biológicas, describe an example of phoresis from Mexican Chiapas Amber, in which a Pseudoscorpion is attached to a Crane Fly.

The Amber-Lagerstätte from Chiapas in southern Mexico: Simojovel, Totolapa, and Estrella de Belén, Late Oligocene to Early Miocene. Schematic map showing the location of the Montecristo mines in Simojovel. Córdova-Tabares et al. (2024).

The specimen described is a piece of amber from the Montecristo Mine at Simojoval in the Colección de Artrópodos Fósiles of the Escuela Nacional de Ciencias Biológicas. The Pseudoscorpion involved is assessed to belong to the genus Hysterochelifer, which has four extant species, but differs from these in the structure of its chelicerae. It is therefore assigned to a new species, Hysterochelifer manpauch, becoming the designated holotype of that species. The specific name 'manpauch' derives from the Tzotzil ‘man pauch’, meaning a person who works with amber.

Hysterochelifer manpauch. (A) Holotype CAF-1 (phoront) and CAF-2 (carrier), general view. (B) CAF-1 in dorsal view; (C) CAF-1 in a closer view. Legs in Roman numerals, abbreviations ab, abdomen; c, carapace; che, chelicera; gt, genitalia pa, patella. Córdova-Tabares et al. (2024).

The Pseudoscorpion is attached to the trochanter (second segment) of the foreleg of a Cranefly assigned to the species Trentepohlia immemorata, one of two species of this genus previously described from Chiapas Amber.

The Pseudoscorpion genus Hysterochelifer belongs to the family Cheliferidae, which is distinguished by having a well-developed venom apparatus in both chelal fingers. The family dates back to the Middle Cretaceous, with the oldest specimen coming from Cenomanian Archingeay Amber, which comes from the Charente Maritime district of south-western France. A protonymph (hatchling) assigned to the Cheliferidae has previously been described from Chiapas Amber, but this is the first adult specimen.

Pseudoscorpions attached as phoronts to other Insects have previously been described from both Baltic and Dominican amber, most commonly targetting Dipterans (True Flies) or Wasps. Living Pseudoscorpions will attach to a variety of organisms, including Vertebrates such as Birds and Mammals, but generally prefer Insects or larger Arachnids, and in particular Beetles. Beetles tend to have fairly specific environmental requirements, as do Pseudoscorpions, so a Pseudoscorpion attaching to a Beetle has a good chance of being carried to a suitable new environment. Flies are more tolerant in their environmental needs, typically settling on a wide range of surfaces, making them less ideal carriers.

Friday, 29 July 2016

Psectrosciara fossilis: A Dung Midge in amber from Chiapas State, Mexico.

Dung Midges, Scatopsidae, are minute True Flies, Diptera with a global distribution. They are a smal group, with about 259 species divided into four subfamilies, which have a very poor fossil record, but which are thought to be very ancient for biogeographical reasons. The Subfamily Psectrosciarinae, for example, is thought to have originated at latest in the Early Jurassic, but to date has yielded not a single fossil anywhere in the world.

In a paper published in the journal Palaeontologica Electronica in July 2016, André Nel and David Coty of the Institut de Systématique,Évolution, Biodiversité at the Muséum national d’Histoirenaturelle describe a Psectrosciarine Dung Midge preserved in amber from the Salt River Mine locality in Chiappas State, Mexico.

The Salt River Mine locality is located on the banks of the Salt River about 70 km southeast of Tuxtla Gutierrez and 1 km north of Totolapa. Amber from this locality has not been accurately dated, but is thought to be between 25 and 15 million years old, making it Late Oligocene to Middle Miocene in age.

The Midge is described as new species, placed in the extant genus Psectrosciara and given the specific name fossilis, indicating that it is the first fossil species in the genus described. The specimen is male, 2.7 mm in length, dark in colour, has ten antennal segments and a wing legth of 1.44 mm.

Psectrosciara fossilisin lateral view. Scale bar is 0.5 mm. Nel & Coty (2016).

Saturday, 8 August 2015

Tityus apozonalli: A new species of Scorpion from Miocene Chiapas Amber.

The ambers of Chiapas State, Mexico, were laid down in the Miocene (and possibly Oligocene) in shallow marine environments. The amber is thought to be derived from resin secreted from a Leguminous tree of the genus Hymenaea, which lived in mangrove forests along the Caribbean shoreline. This amber is almost identical to amber produced in similar mangrove forests during the Miocene in the Dominican Republic and to a lesser extent other parts of the Caribbean, and a thriving, and sometimes illegal, trade in these fossils, combined with poor recording by commercial fossil collectors (particularly those acting illegally) means that fossils in Caribbean amber derived from private collections can be hard to connect to their point of origin. To date two Scorpions have been described from Chiapas Amber, and at least four further specimens attributed to this source are known in private collections, however the exact provenance of these fossils is unclear as precise data on the outcrops which produced them is unavailable.

In a paper published in the journal PLoS One on 5 August 2015, Francisco Riquelme of the Escuela de Estudios Superiores de Jicarero at the Universidad Autónoma del Estado de Morelos, Gabriel Villegas-Guzmán of the Laboratorio de Acarología at the Escuela Nacional de Ciencias Biológicas at the Instituto Politécnico Nacional, Edmundo González-Santillán of the Laboratorio de Aracnología at the Universidad Nacional Autónoma de México, Víctor Córdova-Tabares, also of the Laboratorio de Acarología at the Escuela Nacional de Ciencias Biológicas at the Instituto Politécnico Nacional, Oscar Francke of the Colección Nacional de Arácnidos at the Universidad Nacional Autónoma de Mexico, Dulce Piedra-Jiménez, also of the Laboratorio de Aracnología at the Universidad Nacional Autónoma de México, Emilio Estrada-Ruiz of the Laboratorio de Ecología at the Instituto Politécnico Nacional and Bibiano Luna-Castro of the Museo del Ámbar de Chiapas, describe Scorpion preserved in amber from the Early-Middle Miocene Guadalupe Victoria site near Simojovel in Chiapas, the first known fossil Scorpion that can be confidently assigned to a specific amber-producing site in Chiapas.

The new Scorpion is placed in the large (and probably paraphyletic – not containing all the descendants of the last common ancestor of the group) genus Tityus, within the Family Buthidae, and given the specific name apozonalli, which means ‘sea-bubble’ or ‘sea-foam’ in the Náhuatl language, and which was the term used amber by the pre-Columbian Aztecs.

Tityus apozonalli. (A) Amber piece, arrow indicates the position of fossil inclusion, scale bar 10 mm. (B) General view of fossil Scorpion, scale bar 5 mm. (C) Close view of the specimen, scale bar 2 mm. Riquelme et al. (2015).

Tityus apozonalli is thought to be most closely related to the modern species Tityus clathratus and Tityus columbianus, which are known from the Caribbean Islands, Central America and northern South America, as well as showing features in common with members of the genus from Dominican Amber, and to a lesser extent Tityus knodeli, which is attributed to Chiapas Amber, though of uncertain origin. A single specimen assigned to the genus has been described from Baltic Amber from Europe, Tityus eogenus, however this was described in 1869 and is now missing, and so is considered somewhat dubious.

Friday, 7 November 2014

Two new species of Flat-backed Millipede from Miocene Mexican amber.

Millipedes, Diplopoda, are highly successful soil dwelling Arthropods found in soil in all temperate and tropical regions. They are an ancient group, with a fossil record going back to the Silurian, but this is rather patchy as they appear to have poor preservational potential, and fossil Millipedes are typically only found in Lagerstätten deposits with exceptional preservation of small terrestrial animals, such as ironstone nodules and amber. Millipedes are thought to play a key role in soil formation, and to have played an important role in the development of ecological communities in the soil, so understanding the history of the group is considered important.

In a paper published in the journal PLoS One on 27 August 2014, a team of scientists led by Francisco Riquelme of Posgrado en Ciencias Biológicas and the Instituto de Física at the Universidad Nacional Autónoma de México, describe two new species of Flat-backed Millipedes from amber deposits in northern Chiapas State, Mexico. Chiapas Amber is thought to be between 23 and 15 million years old, and to have been produced in a Mangrove environment by trees of the genus Hymenaea. It is largely collected by artisanal miners.

The first new species is named Maatidesmus paachtun, where ‘Maat’ means ‘amber’ in Mayan, ‘-idesmus’ implies a Flat-backed Millipede and ‘paachtun’ means ‘stoney-backed’ in Mayan. The species is described from a single adult female specimen, preserved three dimensionally in amber.

Maatidesmus paachtun, general view, scale bar is 5 mm. Riquelme et al. (2014).

The specimen is 35.5 mm in length, and comprises the head and all 19 body segments. It has distinctive patterning on the dorsal surface of its body, comprising a large number of tiny lobes (which appear ‘stoney’ to Riquelme et al.), which is not seen in any close living relative.

Maatidesmus paachtun, 3D micro-CT reconstruction. (A–D): General view, scale bar is 5 mm. (E) Head, collum and first segments in lateral view, scale bar is 5 mm. (F) Dorsal view of first segments, scale bar is 2 mm. (G) Ventral view of head with a cross section of first segments, scale bar is 2 mm. (H) Collum, metaterga and paranota in dorsal view, scale bar is 3 mm. (I) Head and legs in dorsal view, scalebar is 3 mm. (J) Last segments in ventral and dorsal view (K), respectively, scale bar is 5 mm. All 3D images are expressed in virtual colours.Anatomical Abbreviations: ant, antennae; cl, collum; ct, cuticle; cw, claw; ep, epiproct; hc, head capsule; hyp, hypoproct; its, inner tissues; l, leg; lgs, longitudinal sulcus of the head capsule; mt, metatergite; mz, metazonite; p, paranota; pap, paraproct; par, preanal ring; pz, prozonite; s, trunk segment;spm, suture between the prozonite and metazonite. Riquelme et al. (2014).

The second new species described is named Anbarrhacus adamantis, where ‘Ánbar’ is Arabic for ‘amber’, ‘-rhacus’ is a common suffix for Millipedes and ‘adamantis’ means ‘diamond’ in Latin, a reference to the rhomboidal sculpting on the dorsal surface of the body segments. The species is described from a single male specimen, 19.8 mm in length, with a head and 17 body segments, preserved three dimensionally in amber.

Anbarrhacus adamantis, general view, scale bar is 5 mm. Riquelme et al. (2014).

Saturday, 11 October 2014

Interpreting the relationship between Ants and Termites from a single piece of Mexican Amber.

Ants and Termites are eusocial Insects that have dominated many tropical ecosystems since at least the Early Cretaceous. Relationships between the two groups (which are not closely related) are complex, with some species able to tolerate one-another and even share nests, while others are deeply hostile, typically with Ants feeding on Termites or Termites fighting to keep all Ants away from their territories. However, while these relationships have been extensively studied in modern representatives of the group, understanding how these Insects may have interacted in the remote past is much more difficult.

In a paper published in the journal PLoS One on 20 August 2014, David Coty of the Muséum National d’Histoire Naturelle in Paris, Cédric Aria of the Department of Natural History-Palaeobiology at the Royal Ontario Museum and the Department of Ecology & Evolutionary Biology at the University of Toronto, and RomainGarrouste, Patricia Wils, Frédéric Legendre and André Nel, also of the of the Muséum National d’Histoire Naturelle in Paris, describe a single piece of amber from the Salt River Amber Mine in Chiapas State, Mexico, which includes several different Ants and Termites, and discuss the implications of this for relationships between the groups.

General configuration of the Mexican amber. (A) Overview of the amber piece, under optical microscope. Scale bar is 3 mm. (B) Three dimensional replica of the same; colours define taxonomic groups, viz. purple for Azteca Ants, blue for Nasutitermes Termites, red for Neivamyrmex Ant, green for small Psocodea. Labels: Az1, Azteca Ant nearest to predation scene; Az2 and Az3, two other Azteca Ants, both trapped in a flow distinct to that of the others inclusions and whose physical density matches that of the Nasutitermes soldier; Na1, Nasutitermes worker trapped between the Neivamyrmex mandibles; Na2, isolated Nasutitermes termite closest to predation scene; Na3, Nasutitermes worker with damaged gaster; Na4, Nasutitermes soldier; Ne, Neivamyrmex Ant; Ps, Psocodea; Scale bar is 3 mm. Aria et al. (2014).

The Amber contains four Termites assigned to a single (unknown) species of the genus Nasutitermes, three workers and a soldier, as well as three Ants of the genus Azteca and one Neivamyrmex Army Ant.

Neivamyrmex, like all Army Ants, are voracious predators, attacking invertebrate and invertebrate prey alike, typically with a sudden attack by a large number of Army Ants overwhelming the prey. Other Ants and Termites are favoured prey for such Insects, and nests will always be attacked when encountered. The Neivamyrmex Ant in the amber has a small worker Termite in its jaws, which suggests that it was engaged in such an attack when it became stuck in, and overwhelmed by, the plant resin which later became preserved as amber. Potentially the Termite could have been seized reflexively by the trapped, dying Ant, or the Ant could have become trapper while trying to scavenge a Termite previously caught in the resin, but one of the other worker Termites shows signs of damage typical of an Army Ant attack suggesting that the two species were fighting before becoming overwhelmed. The presence of a soldier Termite also supports this hypothesis, as in modern members of the genus Nasutitermes, members of this caste remain inside the nest for most of the time, only emerging when the nest is threatened or attacked, and never moving far from the nest.

Details of the Termites. (A) General side view of the NeivamyrmexAnt holding a Nasutitermes Termite (Na1) between its mandibles, under optical microscope, scale bar is 1 mm. (B) Detail of damaged gaster of Nasutitermes worker (Na3) closely contiguous to a Nasutitermes soldier (Na4), scale bar is 1 mm. (C) Side view of closely contiguous Nasutitermes soldier (Na4) and worker (Na3), black arrow: digestive tube of Nasutitermes worker scale bar is 1 mm.Aria et al. (2014).

The situation with the AztecaAnts is more complex. Some modern members of this genus are able to co-occupy the nests of some species of Nasutitermes, on either a seasonal or permanent basis. This is not an entirely benign relationship, as the Ants do consume some of the Termites, but the benefits to the Termites appear to outweigh the costs of removing the Ants; the Termites consume dead Ants, which are a rich source of nitrogen, although they do not actively predate the Ants, and the two species appear to cooperate when defending the nest against mutual threats, such as Army Ants. Aria et al. suggest that the presence of Azteca Ants alongside Nasutitermes Termites that were apparently engaged in defending their nest against an Army Ant attack strongly suggests that such a relationship was occurring in this instance, and that the Ants and Termites were engaged in a defence of a mutual nest against the invading Army Ants.

The precise age of amber from the Salt River Mine has yet to be determined, however it is thought to be at least Middle Miocene in age, suggesting that the mutualistic relationship between Azteca Ants and Nasutitermes Termites is at least that old.