Glyptagnostus reticulatus
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Glyptagnostus reticulatus Temporal range: Paibian |
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| Glyptagnostus reticulatus cephalon | |
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| Glyptagnostus reticulatus pygidium | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | †Trilobita |
| Order: | †Agnostida |
| Family: | †Glyptagnostidae |
| Genus: | †Glyptagnostus |
| Species: | †G. reticulatus |
| Binomial name | |
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Glyptagnostus reticulatus (Angelin, 1851) |
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| Synonyms | |
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Glyptagnostus reticulatus is a species of agnostid trilobite belonging to the genus Glyptagnostus. It existed during the Paibian Age (497 million years ago) of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy. It was characterized by an unusual net-like pattern of furrows on both the cephalon and the pygidium.
Like all members of the suborder Agnostina, Glyptagnostus reticulatus is completely blind and only has two thoracic segments. The cephalon and pygidium are more or less the same size and shape (isopygous). The glabella of the cephalon has two lobes. The front lobe is roughly squarish in shape, while the rear lobe is elongated and split along the middle. The cephalon has a narrow well-defined border. The pygidium has a long tapering central axis which can be divided into three lobes. The axis is connected to the rear margin by a central furrow. At both sides of the axis are a row of four or more pits. The border of the pygidium is also well-defined, widening towards the back, and with short, backward facing marginal spines.
Like other members of the genus, the cephalon always exhibits a pair of kidney-shaped lumps next to the front glabellar lobe. Both the cephalon and the pygidium are highly ornamented with radiating patterns of furrows, resembling a net. The patterns are not perfectly bilaterally symmetrical and can vary between different individuals in the species. They can be distinguished from other members of the genus by irregular patterns of cross furrows that connect the radial furrows. The third pygidial axial lobe is longer than half the length of the second pygidial axial lobe.
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