Many people harbor the false belief that most of the world’s animals have already been discovered. But that’s not the case. According to some estimates, up to seven million species have yet to be named. Given that approximately 1.5 million species have been formally documented to science, that leaves 80% or more waiting to be discovered.
When we start talking about historical species, the number grows even larger.
So, it shouldn’t come as a surprise that a new species of arachnid–dating back to the late Carboniferous period (about 300 million years ago)–was found by a research team at the Mazon Creek fossil beds in Northern Illinois. They recently published their discovery in the Journal of Paleontology.
“The Mazon Creek Fossil-Lagerstätte is rightly famous for the abundance of marine and non-marine fossil biota found in clay ironstone concretions that are collected from the spoil heaps of the old strip mines around Braidwood in northeastern Illinois,” state the authors, led by Paul Selden of the University of Kansas.
Fossils of many extant and extinct arachnid groups have been found at Mazon Creek in the past. What’s surprising about the new discovery, however, is how morphologically unique this spider is.
“The new fossil from Mazon Creek is evidently something very different from any previously described arachnid from either this or any other Coal Measures locality,” say the authors. “It is characterized by its distinctive habitus of an ovate body and robust and very spiny legs. The preserved character combination makes it difficult to place the fossil in any known arachnid order.”
The authors believe that the spines on each of the spider’s eight legs evolved as a defense against predators. They point to spininess in other arthropods of the late Carboniferous era, such as trigonotarbids and millipedes–which didn’t exhibit spines in their earlier relatives, as evidence that spines were an adaptation unique to this period of history.
They also note the resemblance to some living arachnids—including several species of armored harvestmen—which are also believed to exhibit spininess on their legs and body as a degree of protection against predators.
And, while we can only imagine what this fossilized spider might have looked like in real life, we can look to some living “spiny spiders” for clues about its morphology and characteristics. Here are two:
1. Green Lynx Spider
The green lynx spider boasts a vibrant green hue and is typically spotted residing among verdant foliage. The largest member of the Oxyopidae family, this arachnid is prevalent across the southern United States, Mexico, Central America and various islands in the West Indies, notably Jamaica.
Lynx spiders are well-adapted hunters. Eschewing the use of webs to capture their prey, they instead employ a feline-like hunting technique, leaping upon unsuspecting victims. This behavior earns them their name, “lynx spiders.”
Active during daylight hours, these spiders exhibit distinct physical characteristics. Females may reach lengths of up to an inch, while males, more slender in build, typically measure around half an inch. Their legs, ranging from green to yellow, are adorned with lengthy black spines, a common feature among Oxyopidae species, interspersed with dark spots.
2. Spiny Orb-Weaver
The spiny orb-weaver spider, true to its name, boasts a rounded abdomen adorned with numerous spines, resembling the shape of a crab’s shell. These spines, often brightly colored in hues of white, yellow, red, or black, serve as both a form of protection and visual deterrent against potential predators.
Found primarily in tropical and subtropical regions across the globe, including parts of North and South America, Africa and Asia, this species has garnered attention for its striking morphology. In addition to its striking physical attributes, the spiny orb-weaver spider is renowned for its adeptness at constructing intricate orb webs, which it utilizes for prey capture. These webs, meticulously woven with silk threads, feature a characteristic spiral pattern radiating from the center, where the spider patiently awaits its next meal.
The spiny orb-weaver is a small spider, typically ranging from five to nine millimeters in length for females and slightly smaller for males. Their bites are not dangerous to humans.
