Yanjiahe Formation


The Yanjiahe Formation is an Ediacaran to Cambrian fossiliferous geologic formation found in South China.

Dating

The Yanjiahe Formation has been dated through various methods. The top of the formation is dated at and using radiometric dating on ash beds within the area. Likewise, the base of the formation has been dated to between to through carbon isotopic correlations.

Beds

The Yanjiahe Formation consists of five beds. Every bed within the formation contains fossil material.
The beds are as follows, listed by ascending age:
  • Bed 1 is characterized by basal dolomitic conglomerates, with banded black cherts.
  • Bed 2 is mostly consists of siliceous phosphatic dolostone, with flat pebble conglomerates.
  • Bed 3 is characterized by various shales, with the presence of siliceous-phosphatic nodules.
  • Bed 4 is composed of carbonaceous limestones.
  • Bed 5 is characterized by cherts and siliceous phosphatic dolostone, with flat pebble conglomerates.

    Paleobiota

The Yanjiahe Formation contains a wide range of unique organisms from the base of the Cambrian, from Yanjiahella to Beretella, alongside a lot of early molluscs, like Watsonella.

Cnidaria

GenusSpeciesNotesImages
Octapyrgites
  • O. elongatus
Olivooid Medusozoan, larger than any known Olivooid.
Quadrapyrgites
  • O. quadratacris
    		• Olivooid Medusozoan.
    Olivooides
  • Olivooides sp.
  • O. multisulcatus
  • O. mirabilis
    		• Olivooid Medusozoan.
    Pseudooides
  • Pseudooides sp.
    		• Medusozoan.
    Septuconularia
  • S. yanjiaheensis
  • S. crassiformis
    		• Hexangulaconulariid Medusozoan.
    Decimoconularia
  • D. isofacialis
    		• Hexangulaconulariid Medusozoan.
    Carinachites
  • C. spinatus
    		• Cnidarian sclerite, related to the conulariids.
    Cambrorhytium
  • C. major
    		• Elongated cone-like cnidarian.

    Chancelloriida

    GenusSpeciesNotesImages
    Chancelloria
    • Chancelloria sp.
    		Sponge-like eumetazoan.

    Deuterostome

    GenusSpeciesNotesImages
    Protohertzina
    • P. unguliformis
    • P. anabarica
    • P. robusta
    		Possibly a Protoconodont, Paraconodont, or a Chaetognath.
    Tarimspira
  • T. plana
    		• Possible Paraconodont.
    Yunnanodus
  • Yunnanodus sp.
  • Y. yanjiahensis
    		• Possible Paraconodont.
    Yanjiahella
  • Y. biscarpa
    		• Possibly earliest stem group echinoderm.
    Yuknessia
  • Yuknessia sp.
    		• Unbranched pterobranch.
    Hertzina
  • H. guizhouensis
  • H. tenuis
    		• Furnishinid Paraconodont.

    Ecdysozoa

    GenusSpeciesNotesImages
    Beretella
    • B. spinosa
    		Possibly adult or larval ecdysozoan.
    Saccorhytus
  • Saccorhytus sp.
    		• Possibly adult or larval ecdysozoan.

    Lophotrochozoa

    GenusSpeciesNotesImages
    Conotheca
    • C. subcurvata
    • C. obesa
    • C. nana
    • C. transulcata
    		Hyolith lophotrochozoan.
    Hyolithellus
  • H. tenuis?
  • H. decorus
    		• Annelid lophotrochozoan, previously thought to be a Hyolith.
    Lapworthella
  • Lapworthella sp.
    		• Tommotid lophotrochozoan.
    Spinulitheca
  • S. billingsi
    		• Hyolith lophotrochozoan.
    Microcornus
  • M. parvulus?
    		• Hyolith lophotrochozoan.
    Cupitheca
  • C. mira
    		• Hyolith lophotrochozoan.
    Turcutheca
  • T. crasseocochlia
  • T. lubrica
    		• Hyolith lophotrochozoan.
    Lophotheca
  • L. costellata
    		• Hyolith lophotrochozoan.
    Circotheca
  • C. longiconica
  • C. longiconica
    		• Circothecid Hyolith.
    Aldanella
  • A. attleborensis
  • A. yanjiaheensis
    		• Mollusc with a coiled shell.
    Eohalobia
  • E. diadongensis
  • Eohalobia sp.
    		• Halkieriid mollusc.
    Ocruranus
  • Ocruranus sp.
  • O. trulliformis
  • O. finial
    		• Halkieriid mollusc.
    Scenella
  • S. jijiapoensis
    		• Scenellid mollusc.
    Siphogonuchites
  • S. triangularis
    		• Siphogonuchitid mollusc.
    Xianfengella
  • X. ovata
  • X. prima
    		• Mollusc.
    Tuberoconus
  • T. paucipapillae
    		• Mollusc.
    Watsonella
  • W. crosbyi
    		• Mollusc.
    Anabarella
  • A. plana
    		• Helcionelloid mollusc.
    Igorella
  • I. emeiensis
  • I. maidipingensis
  • Igorella sp.
    		• Helcionelloid mollusc.
    Oelandiella
  • O. korobkovi
    		• Helcionelloid mollusc.
    Ceratoconus
  • C. bucers
    		• Helcionelloid mollusc.

    Porifera

    GenusSpeciesNotesImages
    Blastulospongia
    • Blastulospongia sp.
    		Globular demosponge, previously postured to be a radiolarian.
    Hexactinellid spicules
  • ???
    		• A collection of monaxons, diaxons and triaxons.

    ''incertae sedis''

    GenusSpeciesNotesImages
    Anabarites
    • A. trisulcatus
    • A. tianzhushanensis
    • A. gracilis
    • A. ternarius
    		Anabaritid small shelly fossil.
    Tiksitheca
  • T. korobovi
    		• Anabaritid small shelly fossil.
    Cambrotubulus
  • C. decurvatus
    		• Anabaritid small shelly fossil.
    Protoconites
  • P. minor
    		• Curved conical organism, possible relations to Cnidaria.
    Purella
  • P. antiqua
  • P. lepidites
    		• Small shelly fossil.
    Emeiconus
  • E. antiqua
    		• Small shelly fossil.
    Rugatotheca
  • Rugatotheca sp.
    		• Small shelly fossil.
    Coleolella
  • C. recta
    		• Small shelly fossil.
    Vendotaenid
  • Vendotaenia sp.
    		• Ribbon-like organism.
    Torellella
  • T. lentiformis
    		• Tubicolous fossil.

    Flora

    GenusSpeciesNotesImages
    Archaeophycus
    • A. yunnanensis
    		Either a cyanobacteria or the early developmental stage of an alga.
    Konglingiphyton
  • Konglingiphyton sp.
    		• Macroalgae.
    Megathrix
  • M. longus
    		• Filamentous cyanobacterium.
    Myxococcoides
  • Myxococcoides spp.
    		• Cyanobacteria.
    Archaeooides
  • A. granulates
    		• Microalgae.

    Microorganisms

    GenusSpeciesNotesImages
    Asteridium
    • A. tornatum
    		Acritarch.
    Comasphaeridium
  • C. annulare
    		• Acritarch.
    Heliosphaeridium
  • H. ampliatum
    		• Acritarch.
    Micrhystridium
  • M. regulare
    		• Acritarch.
    Yurtusia
  • Y. uniformis
    		• Acritarch.
    Dictyotidium
  • Dictyotidium sp.?
    		• Acritarch.

    Undescribed

    GenusSpeciesNotesImages
    Unnamed probable cnidarian
    • ???
    		Curved tubular organism, possible affinities to cnidarians.