Trilobite - Metcanthina issoumourensis (Asteropyge)
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ITEM # TRILO-Morocco-0020
$200.00
$200.00
per item
Devonian - 395-345 mya
Alnif, Morocco
ITEM # TRILO-Morocco-0020
This is an excellent example of the phacop trilobite Metacanthina issoumourensis from the Devonian of Morocco. Previously called Kayserops or Asteropyge, this Mount Issoumour species has now been described as Metacanthina issoumourensis. A member of the trilobite Order Phacopida, Subfamily Asteropyginae, the species is prized by collectors.
Phacopida ("Lens-face") is an order of trilobite that lived from the Ordovician to the Devonian. It is made up of a morphologically diverse group of related suborders. Hollarops merocristata is a member of the family Acastidae.
The origin of the Phacopida order is uncertain. It comprises three suborders (Phacopina, Calymenina, and Cheirurina) which share a distinctive protaspis (developmental stage lacking segments) type. The Cheirurina and Calymenina retain a rostral plate (an apomorphy) but in virtually all Phacopina the free cheeks are yoked as a single piece. This sort of similarity in development suggests phylogenetic unity. The suborder Calymenina is the most primitive of the Phacopida order and shares some characteristics with the order Ptychopariida, though it is not included in the subclass Libristoma.
Phacopida had 8 to 19 thoracic segments and are distinguishable by the expanded glabella, short or absent preglabellar area, and schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina) eyes. Schizochroal eyes are compound eyes with up to around 700 separate lenses. Each lens has an individual cornea which extended into a rather large sclera. The development of schizochroal eyes in phacopid trilobites is an example of post-displacement paedomorphosis. The eyes of immature holochroal Cambrian trilobites were basically miniature schizochroal eyes. In Phacopida, these were retained, via delayed growth of these immature structures (post-displacement), into the adult form.
This specimen has a dark brown exoskeleton, which contrasts nicely with the light brown-tan matrix. Note the excellent preservation of the eye facets in this trilobite. This specimen measured approximately 2.5 inches long, or 3 inches if measured along its curve.
Alnif, Morocco
ITEM # TRILO-Morocco-0020
This is an excellent example of the phacop trilobite Metacanthina issoumourensis from the Devonian of Morocco. Previously called Kayserops or Asteropyge, this Mount Issoumour species has now been described as Metacanthina issoumourensis. A member of the trilobite Order Phacopida, Subfamily Asteropyginae, the species is prized by collectors.
Phacopida ("Lens-face") is an order of trilobite that lived from the Ordovician to the Devonian. It is made up of a morphologically diverse group of related suborders. Hollarops merocristata is a member of the family Acastidae.
The origin of the Phacopida order is uncertain. It comprises three suborders (Phacopina, Calymenina, and Cheirurina) which share a distinctive protaspis (developmental stage lacking segments) type. The Cheirurina and Calymenina retain a rostral plate (an apomorphy) but in virtually all Phacopina the free cheeks are yoked as a single piece. This sort of similarity in development suggests phylogenetic unity. The suborder Calymenina is the most primitive of the Phacopida order and shares some characteristics with the order Ptychopariida, though it is not included in the subclass Libristoma.
Phacopida had 8 to 19 thoracic segments and are distinguishable by the expanded glabella, short or absent preglabellar area, and schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina) eyes. Schizochroal eyes are compound eyes with up to around 700 separate lenses. Each lens has an individual cornea which extended into a rather large sclera. The development of schizochroal eyes in phacopid trilobites is an example of post-displacement paedomorphosis. The eyes of immature holochroal Cambrian trilobites were basically miniature schizochroal eyes. In Phacopida, these were retained, via delayed growth of these immature structures (post-displacement), into the adult form.
This specimen has a dark brown exoskeleton, which contrasts nicely with the light brown-tan matrix. Note the excellent preservation of the eye facets in this trilobite. This specimen measured approximately 2.5 inches long, or 3 inches if measured along its curve.
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