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.

Talacasto Formation
Stratigraphic range: Devonian
Type	Geological formation
Unit of	Gualilán Group
Thickness	300–1,000 m (980–3,280 ft)
Location
Region	San Juan Province La Rioja Province
Country	Argentina
Extent	Precordillera Basin
Type section
Named by	Padula et al
Year defined	1967

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.^[1][2] Along with the Punta Negra Formation, it makes up the Gualilán Group, which represent Devonian-aged deposits in the Argentine Precordillera.^[3] 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.^[1]

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	Images
Actinopteria[4]	A. eschwegei	Loma de los Piojos	About 20 specimens	A pterineid
	A. modesta	Loma de los Piojos	Several specimens	A pterineid
Anthracoleda[4]	A. (Pseudoleda) minuta	Cerro del Fuerte Loma de los Piojos	Several specimens	A nuculanid
Deceptrix[4]	D. (Devonodeceptrix) jachalensis	Loma de los Piojos	Several specimens	A cardiolariid
Glossites[4]	G. cf. G. depressus	Loma de los Piojos	2 specimens	A modiomorphid
Grammysioidea[4]	G. capricornus	Loma de los Piojos	5 specimens	A grammysiid
Nuculites[4]	N. argentinum	Cerro del Fuerte Loma de los Piojos	Numerous specimens	A cucullellid
Nuculoidea[4]	N.? sp.	Cerro del Fuerte	4 specimens	A nuculid
Palaeoneilo[4]	P. cf. P. forbesi	Loma de los Piojos	5 internal moulds	A malletiid
Pholadella[4]	P. radiata	Loma de los Piojos	7 specimens	A sanguinolitid

Brachiopods

Brachiopods reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Anoplia[5][6]	A. azucenae	Portezuelo del Tambolar	Over 70 specimens	An anopliid
	A. sp. A	Río Talacasto	6 specimens	An anopliid
	A. sp.	Los Algarrobos section		An anopliid
Athyris[6]	A. sp.	Los Algarrobos section		An athyridid
Australostrophia[5]	A. penoensis	Loma de los Piojos Cerro del Fuerte Agua del Peñón	Numerous specimens	A strophochonetid
Boucotia[7]	B. argentina	Loma de los Piojos Portezuelo del Tambolar	3 isolated valves	A notanopliid
Chonostrophia[5][8]	C. elenae	Loma de los Piojos	Several specimens	A chonostrophiid
	C. reversa var. andina	Quebrada de Talacasto	Several specimens	Tentatively reclassified as a species of Sanjuanetes[9]
Eoschucertella[10]	E. delicata	Quebrada Zerina	Numerous specimens	An areostrophiid
Iridistrophia[10]	I. aliciae	Cerro del Fuerte	Numerous specimens	A chilidiopsid
	I. dominans	Loma de los Piojos	Numerous specimens	A chilidiopsid
	I. magna	Cordón de Agua de Peñón	Numerous specimens	A chilidiopsid
	I. prima	Quebrada La Cortadera	Numerous specimens	A chilidiopsid
Kentronetes[5]	K. giolittii	Quebrada Las Loras	6 valves	A strophochonetid
	K. ortegae	Loma de los Piojos	Numerous specimens	A strophochonetid
	K. vallensis	Loma de los Piojos	31 specimens	A strophochonetid
	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[6]	L. sp.	Los Algarrobos section		A lingulid
Lomaella[5]	L. primoris	Loma de los Piojos	9 specimens	An eodevonariid
	L. sanjuanina	Loma de los Piojos	Several specimens	An eodevonariid
Meristella[6]	M. sp.	Los Algarrobos section		A meristellid
Metaplasia[6]	M. baldisi	Los Algarrobos section		An ambocoeliid
Pleurochonetes[5]	?P. sp.	Loma de los Piojos	32 specimens	A chonetid
Plicanoplia[5]	P. sp.	Loma de los Piojos	5 specimens	An anopliid
Sanjuanetes[5][6][8]	?S. andina	Quebrada de Talacasto Los Algarrobos section	Several specimens	A strophochonetid, originally reported as Chonostrophia reversa var. andina[9]

Cephalopods

Cephalopods reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Bactrites[1]	B. gracilis	Quebrada de Talacasto Below Keidel's Bed	18 specimens	A bactritid
	B. sp.	Quebrada de Talacasto Sierra de las Minitas	5 specimens	A bactritid
Devonobactrites[1]	D.? sp.	Loma de los Piojos section	2 specimens	A bactritid

Corals

Corals reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Enterolasma[6]	E. sp.	Cerro del Fuerte section	Fragments & complete specimens	A horn coral
Favosites[6]	F.? sp.	Cerro del Fuerte section	1 colony	A tabulate coral
Parastriatopora[6][11]	P. cf. gigantea	Tambolar section	6 small branch fragments	A tabulate coral
	P. sanjuanina	Los Algarrobos section		A tabulate coral
	P. sp.	Los Algarrobos section		A tabulate coral

Echinoderms

Echinoderms reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Argentinaster[12]	A. bodenbenderi	Jachal	Several specimens	An ophiurinid brittle star
Crinoidea indet.[6]	Indeterminate	Los Algarrobos section		A crinoid
Furcaster[12]	F. separatus	Jachal	Multiple specimens	A protasterid brittle star
Marginix[12]	M. yachalensis	Jachal	Several specimens	An encrinasterid brittle star
Promopalaeaster[12]	P.? quadriserialis	Jachal	Several specimens	A valvatid starfish

Hyoliths

Hyoliths reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Hyolithida indet.[6]	Indeterminate	Los Algarrobos section		A hyolithid

Ostracods

Ostracods reported from the Talacasto Formation
Genus	Species	Presence	Material	Notes	Images
Aechmina[13]	A. sp.	Talacasto Creek	6 specimens	A member of Podocopa
Amphizona[13]	A.? argentinensis	Portezuelo del Tambolar Talacasto Creek Poblete Sur Las Tunas	23 specimens	A member of Podocopa
Bollia[13]	B. talacastensis	Talacasto Creek Poblete Sur	20 specimens	A member of Podocopa
Keslingiella[13]	K. teresae	Los Algarrobos Talacasto Creek Poblete Sur La Chilcas Las Tunas	Several specimens	A member of Podocopida
Lapazites[13]	L. aff. L. trinodis	Portezuelo del Tambolar La Cortadera Poblete Sur La Chilca	12 specimens	A member of Podocopa
Petrisigmoopsis[13]	P.? rotundum	Talacasto Creek La Chilca	Several specimens	A member of Podocopa
Pircawayra[13][14]	P. antiqua	Portezuelo del Tambolar La Cortadera Creek La Chilca Las Aguaditas Creek	5 specimens	A member of Palaeocopida
	P. peregrina	Loma de los Piojos	Several specimens	A member of Palaeocopida
Suinella[13]	S. huarpesi	Portezuelo del Tambolar Talacasto Creek Poblete Sur	Several specimens	A member of Podocopa
Thlipsurella[13]	T. aff. T. putea	Los Algarrobos Talacasto Creek Poblete Sur Las Tunas	33 specimens	A member of Podocopida
Ulrichia[13]	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[15]	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	Images
Aguaditaspis[16]	A. mediaspina	Quebrada de las Aguaditas Sierra de las Minitas	Several specimens	A dalmanitid
Bainella[17]	B. cooperi	Cerro La Chilca	6 specimens	A calmoniid
	B. sanjuanina	Cerro La Chilca	8 specimens	A calmoniid
Calmonia[17]	C. nov. sp. A	Loma de los Piojos	An internal mould (CORD PZ 8613)	A calmoniid
Dalmanitoides[18]	D. boehmi	Loma de los Piojos	Several specimens	A dalmanitid
	D. drevermanni	Loma de los Piojos Cerro La Chilca	Several specimens	A dalmanitid
Dalmanitidae indet.[6][16]	Gen. et. sp. nov.	Quebrada de las Aguaditas	One specimen (CEGH-UNC 27422)	An unnamed dalmanitid
	Indeterminate	Los Algarrobos section		A dalmanitid
Dalmanitinae gen. et. sp. indet.[2]	Indeterminate	Sierra de las Minitas	Fragmentary pygidium (PULR-132 A-B)	A dalmanitid
Deltacephalaspis[17]	D. sp.	Cerro La Chilca	2 specimens	A calmoniid
Echidnops[2][19]	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[16]	I. leonorae	Quebrada de Las Aguaditas Quebrada de Talacasto Loma de los Piojos	Several specimens	A dalmanitid
Maurotarion[6][20][21]	M. (Malvinotarion) gaucho	Loma de los Piojos	10 specimens	An aulacopleurid
	M. (Malvinotarion) haudei	Loma de los Piojos	2 specimens	An aulacopleurid
	M. (Malvinotarion) talacastoense	La Cantera point	5 specimens	An aulacopleurid
	M. (Malvinotarion) sp.	Portezuelo del Tambolar	One specimen (CEGH-UNC 7.086)	An aulacopleurid
	M. (Malvinotarion) sp. B	Cerro La Chilca	One specimen	An aulacopleurid
	M. megacephalum	Loma de los Piojos	23 specimens	An aulacopleurid
	M. sp.	Los Algarrobos section		An aulacopleurid
Paciphacops[2][6]	P. (Paciphacops) sp.	Sierra de las Minitas	Several specimens	Now known as Echidnops taphomimus[19]
	P. sp.	Los Algarrobos section		A phacopid
	P.? sp.	Sierra de las Minitas	One specimen (PULR-127 A-B)	A phacopid
Parabouleia[6][22]	P. eldredgei	Quebrada de Talacasto	9 specimens	A calmoniid
	P. sp.	Los Algarrobos section		A calmoniid
Talacastops[2][22]	T. zarelae	Quebrada de Las Aguaditas Sierra de las Minitas	Multiple specimens	A calmoniid
Tarijactinoides[17]	T. jarcasensis	Cerro La Chilca Loma de los Piojos	13 specimens	A calmoniid
Tormesiscus[2]	T. cf. hildae	Sierra de las Minitas	Partial specimen (PULR-130)	A calmoniid
Unguliproetus[2]	U.? sp.	Sierra de las Minitas	Two associated fragments	A proetid