# Talacasto Formation

The Talacasto Formation is a geological formation in Argentina, exposed primarily across San Juan Province, with an additional outcrop in La Rioja Province. It preserves fossils dating back to the Devonian period.

## Description

The Talacasto Formation is exposed in the Precordillera Basin of Argentina, with outcrops most widespread in San Juan Province, though an isolated exposure also exists at Sierra de las Minitas in La Rioja Province. Along with the Punta Negra Formation, it makes up the Gualilán Group, which represent Devonian-aged deposits in the Argentine Precordillera. The thickness of the Talacasto Formation varies across its extent; at the type locality of Quebrada de Talacasto in the south it is 300 m (980 ft) thick, while at the Loma de los Piojos section near the Jáchal River in the north it exceeds 1,000 m (3,300 ft) in thickness.

## Fossil content

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |

### Bivalves

Bivalves reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Actinopteria | A. eschwegei | Loma de los Piojos | About 20 specimens | A pterineid |
| Actinopteria | A. modesta | Loma de los Piojos | Several specimens | A pterineid |
| Anthracoleda | A. (Pseudoleda) minuta | Cerro del Fuerte Loma de los Piojos | Several specimens | A nuculanid |
| Deceptrix | D. (Devonodeceptrix) jachalensis | Loma de los Piojos | Several specimens | A cardiolariid |
| Glossites | G. cf. G. depressus | Loma de los Piojos | 2 specimens | A modiomorphid |
| Grammysioidea | G. capricornus | Loma de los Piojos | 5 specimens | A grammysiid |
| Nuculites | N. argentinum | Cerro del Fuerte Loma de los Piojos | Numerous specimens | A cucullellid |
| Nuculoidea | N.? sp. | Cerro del Fuerte | 4 specimens | A nuculid |
| Palaeoneilo | P. cf. P. forbesi | Loma de los Piojos | 5 internal moulds | A malletiid |
| Pholadella | P. radiata | Loma de los Piojos | 7 specimens | A sanguinolitid |

### Brachiopods

Brachiopods reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Anoplia | A. azucenae | Portezuelo del Tambolar | Over 70 specimens | An anopliid |
| Anoplia | A. sp. A | Río Talacasto | 6 specimens | An anopliid |
| Anoplia | A. sp. | Los Algarrobos section | | An anopliid |
| Athyris | A. sp. | Los Algarrobos section | | An athyridid |
| Australostrophia | A. penoensis | Loma de los Piojos Cerro del Fuerte Agua del Peñón | Numerous specimens | A strophochonetid |
| Boucotia | B. argentina | Loma de los Piojos Portezuelo del Tambolar | 3 isolated valves | A notanopliid |
| Chonostrophia | C. elenae | Loma de los Piojos | Several specimens | A chonostrophiid |
| Chonostrophia | C. reversa var. andina | Quebrada de Talacasto | Several specimens | Tentatively reclassified as a species of Sanjuanetes |
| Eoschucertella | E. delicata | Quebrada Zerina | Numerous specimens | An areostrophiid |
| Iridistrophia | I. aliciae | Cerro del Fuerte | Numerous specimens | A chilidiopsid |
| Iridistrophia | I. dominans | Loma de los Piojos | Numerous specimens | A chilidiopsid |
| Iridistrophia | I. magna | Cordón de Agua de Peñón | Numerous specimens | A chilidiopsid |
| Iridistrophia | I. prima | Quebrada La Cortadera | Numerous specimens | A chilidiopsid |
| Kentronetes | K. giolittii | Quebrada Las Loras | 6 valves | A strophochonetid |
| Kentronetes | K. ortegae | Loma de los Piojos | Numerous specimens | A strophochonetid |
| Kentronetes | K. vallensis | Loma de los Piojos | 31 specimens | A strophochonetid |
| Kentronetes | K. variabilis | Portezuelo del Tambolar Poblete Sur Quebrada del río Talacasto Quebrada del Chañar (Cerro La Chilca) Loma de los Piojos | 32 valves | A strophochonetid |
| Lingula | L. sp. | Los Algarrobos section | | A lingulid |
| Lomaella | L. primoris | Loma de los Piojos | 9 specimens | An eodevonariid |
| Lomaella | L. sanjuanina | Loma de los Piojos | Several specimens | An eodevonariid |
| Meristella | M. sp. | Los Algarrobos section | | A meristellid |
| Metaplasia | M. baldisi | Los Algarrobos section | | An ambocoeliid |
| Pleurochonetes | ?P. sp. | Loma de los Piojos | 32 specimens | A chonetid |
| Plicanoplia | P. sp. | Loma de los Piojos | 5 specimens | An anopliid |
| Sanjuanetes | ?S. andina | Quebrada de Talacasto Los Algarrobos section | Several specimens | A strophochonetid, originally reported as Chonostrophia reversa var. andina |

### Cephalopods

Cephalopods reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Bactrites | B. gracilis | Quebrada de Talacasto Below Keidel's Bed | 18 specimens | A bactritid |
| Bactrites | B. sp. | Quebrada de Talacasto Sierra de las Minitas | 5 specimens | A bactritid |
| Devonobactrites | D.? sp. | Loma de los Piojos section | 2 specimens | A bactritid |

### Corals

Corals reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Enterolasma | E. sp. | Cerro del Fuerte section | Fragments & complete specimens | A horn coral |
| Favosites | F.? sp. | Cerro del Fuerte section | 1 colony | A tabulate coral |
| Parastriatopora | P. cf. gigantea | Tambolar section | 6 small branch fragments | A tabulate coral |
| Parastriatopora | P. sanjuanina | Los Algarrobos section | | A tabulate coral |
| Parastriatopora | P. sp. | Los Algarrobos section | | A tabulate coral |

### Echinoderms

Echinoderms reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Argentinaster | A. bodenbenderi | Jachal | Several specimens | An ophiurinid brittle star |
| Crinoidea indet. | Indeterminate | Los Algarrobos section | | A crinoid |
| Furcaster | F. separatus | Jachal | Multiple specimens | A protasterid brittle star |
| Marginix | M. yachalensis | Jachal | Several specimens | An encrinasterid brittle star |
| Promopalaeaster | P.? quadriserialis | Jachal | Several specimens | A valvatid starfish |

### Hyoliths

Hyoliths reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Hyolithida indet. | Indeterminate | Los Algarrobos section | | A hyolithid | |

### Ostracods

Ostracods reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Aechmina | A. sp. | Talacasto Creek | 6 specimens | A member of Podocopa |
| Amphizona | A.? argentinensis | Portezuelo del Tambolar Talacasto Creek Poblete Sur Las Tunas | 23 specimens | A member of Podocopa |
| Bollia | B. talacastensis | Talacasto Creek Poblete Sur | 20 specimens | A member of Podocopa |
| Keslingiella | K. teresae | Los Algarrobos Talacasto Creek Poblete Sur La Chilcas Las Tunas | Several specimens | A member of Podocopida |
| Lapazites | L. aff. L. trinodis | Portezuelo del Tambolar La Cortadera Poblete Sur La Chilca | 12 specimens | A member of Podocopa |
| Petrisigmoopsis | P.? rotundum | Talacasto Creek La Chilca | Several specimens | A member of Podocopa |
| Pircawayra | P. antiqua | Portezuelo del Tambolar La Cortadera Creek La Chilca Las Aguaditas Creek | 5 specimens | A member of Palaeocopida |
| Pircawayra | P. peregrina | Loma de los Piojos | Several specimens | A member of Palaeocopida |
| Suinella | S. huarpesi | Portezuelo del Tambolar Talacasto Creek Poblete Sur | Several specimens | A member of Podocopa |
| Thlipsurella | T. aff. T. putea | Los Algarrobos Talacasto Creek Poblete Sur Las Tunas | 33 specimens | A member of Podocopida |
| Ulrichia | U. sp. | Talacasto Creek Poblete Sur La Chilca | 7 specimens | A member of Podocopa |

### Sponges

Sponges reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes | Images |
| Talacastospongia | T. minima | Talacasto section Los Algarrobos Las Aguaditas | 13 specimens | A glass sponge | |

### Trilobites

Trilobites reported from the Talacasto Formation :
| Genus | Species | Presence | Material | Notes |
| Aguaditaspis | A. mediaspina | Quebrada de las Aguaditas Sierra de las Minitas | Several specimens | A dalmanitid |
| Bainella | B. cooperi | Cerro La Chilca | 6 specimens | A calmoniid |
| Bainella | B. sanjuanina | Cerro La Chilca | 8 specimens | A calmoniid |
| Calmonia | C. nov. sp. A | Loma de los Piojos | An internal mould (CORD PZ 8613) | A calmoniid |
| Dalmanitoides | D. boehmi | Loma de los Piojos | Several specimens | A dalmanitid |
| Dalmanitoides | D. drevermanni | Loma de los Piojos Cerro La Chilca | Several specimens | A dalmanitid |
| Dalmanitidae indet. | Gen. et. sp. nov. | Quebrada de las Aguaditas | One specimen (CEGH-UNC 27422) | An unnamed dalmanitid |
| Dalmanitidae indet. | Indeterminate | Los Algarrobos section | | A dalmanitid |
| Dalmanitinae gen. et. sp. indet. | Indeterminate | Sierra de las Minitas | Fragmentary pygidium (PULR-132 A-B) | A dalmanitid |
| Deltacephalaspis | D. sp. | Cerro La Chilca | 2 specimens | A calmoniid |
| Echidnops | E. taphomimus | Quebrada de Las Aguaditas Sierra de Los Blaquitos Sierra de las Minitas | 12 specimens | A phacopid, originally reported as an unnamed species of Paciphacops |
| Ivanites | I. leonorae | Quebrada de Las Aguaditas Quebrada de Talacasto Loma de los Piojos | Several specimens | A dalmanitid |
| Maurotarion | M. (Malvinotarion) gaucho | Loma de los Piojos | 10 specimens | An aulacopleurid |
| Maurotarion | M. (Malvinotarion) haudei | Loma de los Piojos | 2 specimens | An aulacopleurid |
| Maurotarion | M. (Malvinotarion) talacastoense | La Cantera point | 5 specimens | An aulacopleurid |
| Maurotarion | M. (Malvinotarion) sp. | Portezuelo del Tambolar | One specimen (CEGH-UNC 7.086) | An aulacopleurid |
| Maurotarion | M. (Malvinotarion) sp. B | Cerro La Chilca | One specimen | An aulacopleurid |
| Maurotarion | M. megacephalum | Loma de los Piojos | 23 specimens | An aulacopleurid |
| Maurotarion | M. sp. | Los Algarrobos section | | An aulacopleurid |
| Paciphacops | P. (Paciphacops) sp. | Sierra de las Minitas | Several specimens | Now known as Echidnops taphomimus |
| Paciphacops | P. sp. | Los Algarrobos section | | A phacopid |
| Paciphacops | P.? sp. | Sierra de las Minitas | One specimen (PULR-127 A-B) | A phacopid |
| Parabouleia | P. eldredgei | Quebrada de Talacasto | 9 specimens | A calmoniid |
| Parabouleia | P. sp. | Los Algarrobos section | | A calmoniid |
| Talacastops | T. zarelae | Quebrada de Las Aguaditas Sierra de las Minitas | Multiple specimens | A calmoniid |
| Tarijactinoides | T. jarcasensis | Cerro La Chilca Loma de los Piojos | 13 specimens | A calmoniid |
| Tormesiscus | T. cf. hildae | Sierra de las Minitas | Partial specimen (PULR-130) | A calmoniid |
| Unguliproetus | U.? sp. | Sierra de las Minitas | Two associated fragments | A proetid |