It's probably a black widow and yes very poisonous.
If you found a spider that is black, not fuzzy and has a yellow design on its back, his could mean that you found a banana spider. These are common in Oklahoma.
a spider known as a cross spider usaually found in the uk
you have found aRED BACK SPIDER! watch out. poisonous
The spider that is black with a white crescent on its back is the Brown House Spider. This spider is often confused with the red-back spider.
A black widow spider is black with a red mark on it's abdomen; this might or might not be what you meant. The black widow sometimes has a red mark on her back, as well. The red backed spider of Australia, a relative of the black widow, has an orange red mark on the back.
A black spider that has a red stripe on the back is possibly a red spotted ant mimic spider. They walk on six legs instead of eight and can be found in Arizona.
You have to identify it.
A black spider with a red mark and green fangs might be a black widow spider. This spider is very venomous and its bite can kill a human if treatment is not received soon after a bite.
The Sydney Funnel web spider is the most dangerous. the Goliath spider is not dangerousThe "Black Widow". It is an all black spider with a red hourglass shape on its underside. One bite and you will die within and hour. It injects so much venom in one bite that it can kill 6-7 adults.
Its a tobyotter.it is found in north india...
The spider you are describing is mainly found in Australia. Its called a red back. Very Very Poisonous.
The Orb Weaver is the spider with an orange back and black diamonds on its back. It is not aggressive and not venomous.