The discovery of a rare spider not seen in more than 30 years has halted a San Antonio highway construction project indefinitely.

The San Antonio Express-News reports the Braken Bat Cave meshweaver was discovered in the middle of a $15 million underpass project on Texas 151 at Loop 1604 in northwestern San Antonio.

Biologist Jean Krejca of Zara Environmental, a consultant for the Texas Department of Transportation on the project, says the spider, which is about the size of a dime, was found after rain exposed a six-foot-deep natural hole on the highway median.

The eyeless spider has been on the federal endangered species list since 2000, and the habitat is protected.